- Post-Effective Amendment (investment company, rule 485(b)) (485BPOS)

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549


Form N-1A

REGISTRATION STATEMENT (NO. 33-49023)
UNDER THE SECURITIES ACT OF 1933	[X]
Pre-Effective Amendment No.	[ ]
Post-Effective Amendment No. 24	[X]
and

REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940

Amendment No. 25 [X]

VANGUARD ADMIRAL FUNDS

(Exact Name of Registrant as Specified in Declaration of Trust)

P.O. Box 2600, Valley Forge, PA 19482

(Address of Principal Executive Office)

Registrant’s Telephone Number (610) 669-1000

Heidi Stam, Esquire

P.O. Box 876

Valley Forge, PA 19482

Approximate Date of Proposed Public Offering:

It is proposed that this filing will become effective (check appropriate box)

[ ] immediately upon filing pursuant to paragraph (b)

[x] on December 23, 2009 pursuant to paragraph (b)

[ ] 60 days after filing pursuant to paragraph (a)(1)

[ ] on (date) pursuant to paragraph (a)(1)

[ ] 75 days after filing pursuant to paragraph (a)(2)

[ ] on (date) pursuant to paragraph (a)(2) of rule 485

If appropriate, check the following box:

[ ] This post-effective amendment designates a new effective date for a

previously filed post-effective amendment.

Vanguard Federal Money Market Fund

Supplement to the Prospectus Dated December 29, 2008

Important Changes to Vanguard Federal Money Market Fund

Effective at the close of business on June 2, 2009, Vanguard Federal Money Market Fund (the “Fund”) will no longer open new accounts for individual investors, and it will no longer be available as a new investment option for defined contribution plans. In addition, the Fund will no longer open new accounts for, or accept additional investments from, any other financial advisor, intermediary, or institutional investors. There is no specific time frame for when the Fund will reopen.

Participants in defined contribution plans that offered the Fund as of June 2, 2009, may continue to invest in the Fund for a brief transition period.

During the Fund’s closed period, current retail shareholders may continue to purchase, exchange, or redeem shares of the Fund online, by telephone, or by mail.

The Fund may modify these transaction policies at any time and without prior notice to shareholders. You may call Vanguard for more detailed information about the Fund’s transaction policies. Participants in employer-sponsored plans may call Vanguard Participant Services at 800-523-1188. Investors in nonretirement accounts and IRAs may call Vanguard’s Investor Information Department at 800-662-7447.


© 2009 The Vanguard Group, Inc. All rights reserved.
Vanguard Marketing Corporation, Distributor.	PSFC33_062009

Vanguard Money Market Funds

Supplement to the Prospectus Dated December 29, 2008

Reorganization of Vanguard Treasury Money Market Fund into Vanguard Admiral™ Treasury Money Market Fund

Effective at the opening of business on August 11, 2009, the reorganization of Vanguard Treasury Money Market Fund into Vanguard Admiral Treasury Money Market Fund is complete. Any references to Vanguard Treasury Money Market Fund in this prospectus are hereby deleted.

Important Note Regarding Vanguard Admiral Treasury Money Market Fund

Vanguard Admiral Treasury Money Market Fund (the Fund) will no longer accept additional investments from any financial advisor, intermediary, or institutional accounts, including those of defined contribution plans. Furthermore, the Fund is no longer available as an investment option for defined contribution plans.

The Fund is closed to new accounts and will remain closed until further notice. During the Fund’s closed period, existing retail shareholders may continue to purchase, exchange, or redeem shares of the Fund online, by telephone, or by mail.

The Fund may modify these transaction policies at any time without prior notice to shareholders. You may call Vanguard for more detailed information about the Fund’s transaction policies. Participants in employer-sponsored plans may call Vanguard Participant Services at 800-523-1188. Investors in nonretirement accounts and IRAs may call Vanguard’s Investor Information Department at 800-662-7447.


© 2009 The Vanguard Group, Inc. All rights reserved.
Vanguard Marketing Corporation, Distributor.	PSMG30 082009

Vanguard Money Market Funds Prospectus

December 23, 2009

Investor Shares

Vanguard Prime Money Market Fund (VMMXX)

Vanguard Federal Money Market Fund (VMFXX)

Vanguard Admiral™ Treasury Money Market Fund (VUSXX)

This prospectus contains financial data for the Funds through the fiscal year ended August 31, 2009 .

The Securities and Exchange Commission has not approved or disapproved these securities or passed upon the adequacy of this prospectus. Any representation to the contrary is a criminal offense.


Contents


Vanguard Fund Summaries		Financial Highlights	23
Prime Money Market Fund	1	Investing With Vanguard	27
Federal Money Market Fund	5	Purchasing Shares	27
Admiral Treasury Money Market Fund	9	Converting Shares	30
More on the Funds	13	Redeeming Shares	31
The Funds and Vanguard	19	Exchanging Shares	34
Investment Advisor	19	Other Rules You Should Know	35
Dividends and Taxes	20	Fund and Account Updates	39
Share Price	22	Contacting Vanguard	41
		Additional Information	42
		Glossary of Investment Terms	43

Vanguard Prime Money Market Fund

Investment Objective

The Fund seeks to provide current income while maintaining liquidity and a stable share price of $1.

Fees and Expenses

The following tables describe the fees and expenses you may pay if you buy and hold Investor Shares of the Fund.


Shareholder Fees
(Fees paid directly from your investment)
Sales Charge (Load) Imposed on Purchases	None
Purchase Fee	None
Sales Charge (Load) Imposed on Reinvested Dividends	None
Redemption Fee	None
Account Service Fee (for fund account balances below $10,000)	$20/year


Annual Fund Operating Expenses
(Expenses that you pay each year as a percentage of the value of your investment)
Management Expenses	0.21%
12b-1 Distribution Fee	None
Other Expenses	0.04%
Total Annual Fund Operating Expenses	0.25% ¹

1 The Total Annual Fund Operating Expenses have been restated to reflect current expenses that no longer include fees for participation in the Treasury Money Market Fund Guarantee Program, which the U.S. Treasury Department discontinued as of September 18, 2009. Vanguard and the Fund’s Board have agreed to temporarily limit certain net operating expenses in excess of the Fund’s daily yield so as to maintain a zero or positive yield for the Fund. Vanguard and the Fund’s Board may terminate the temporary expense limitation at any time.

Example

The following example is intended to help you compare the cost of investing in the Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invest $10,000 in the Fund’s shares. This example assumes that the Shares provide a return of 5% a year and that operating expenses remain the same. The results apply whether or not you redeem your investment at the end of the given period. Although your actual costs may be higher or lower, based on these assumptions your costs would be:


1 Year	3 Years	5 Years	10 Years
$26	$80	$141	$318

Primary Investment Policies

The Fund invests primarily in high-quality, short-term money market instruments, including certificates of deposit, banker’s acceptances, commercial paper, and other money market securities. To be considered high-quality, a security generally must be rated in one of the two highest credit-quality categories for short-term securities by at least two nationally recognized rating services (or by one, if only one rating service has rated the security). If unrated, the security must be determined by Vanguard to be of quality equivalent to securities in the two highest credit-quality categories. The Fund invests more than 25% of its assets in securities issued by companies in the financial services industry. The Fund maintains a dollar-weighted average maturity of 90 days or less.

Primary Risks

The Fund is designed for investors with a low tolerance for risk; however, the Fund’s performance could be hurt by:

• Income risk , which is the chance that the Fund’s income will decline because of falling interest rates. Because the Fund’s income is based on short-term interest rates—which can fluctuate significantly over short periods—income risk is expected to be high.

• Manager risk , which is the chance that poor security selection will cause the Fund to underperform relevant benchmarks or other funds with a similar investment objective.

• Credit risk , which is the chance that the issuer of a security will fail to pay interest and principal in a timely manner, or that negative perceptions of the issuer’s ability to make such payments will cause the price of that security to decline. Credit risk should be very low for the Fund, because it invests primarily in securities that are considered to be of high quality.

• Industry concentration risk , which is the chance that there will be overall problems affecting a particular industry. Because the Fund invests more than 25% of its assets in securities issued by companies in the financial services industry, the Fund’s performance depends to a greater extent on the overall condition of that industry.

An investment in the Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. Although the Fund seeks to preserve the value of your investment at $1 per share, it is possible to lose money by investing in the Fund.

Annual Total Returns

The following bar chart and table are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund's Investor Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Fund's Investor Shares compare with those of a relevant market index and a comparative benchmark. The last line item in the table is derived from data provided by Lipper Inc. Keep in mind that the Fund’s past performance does not indicate how the Fund will perform in the future. Updated performance information is available on our website at www.vanguard.com or by calling Vanguard toll-free at 800-662-7447.

Annual Total Returns—Investor Shares ¹

1 The year-to-date return as of the most recent calendar quarter, which ended September 30, 2009, was 0.50%.

During the periods shown in the bar chart, the highest return for a calendar quarter was 1.61% (quarter ended September 30, 2000), and the lowest return for a quarter was 0.19% (quarter ended March 31, 2004).


Average Annual Total Returns for Periods Ended December 31, 2008
	1 Year	5 Years	10 Years
Vanguard Prime Money Market Fund Investor Shares	2.77%	3.37%	3.48%
Comparative Benchmarks
Citigroup 3-Month U.S. Treasury Bill Index
(reflects no deduction for fees or expenses)	1.80%	3.10%	3.30%
Money Market Funds Average	2.04	2.73	2.86

Investment Advisor

The Vanguard Group, Inc.

Portfolio Manager

David R. Glocke, Principal of Vanguard. He has managed the Fund since 2003.

Purchase and Sale of Fund Shares

You may purchase or redeem shares online through our website at www.vanguard.com , by mail (The Vanguard Group, P.O. Box 1100, Valley Forge, PA 19482-1110), or by telephone (800-662-2739). The following table provides the Fund’s minimum initial and subsequent investment requirements .

Account Minimums

To open and maintain an account To add to an existing account

Investor Shares

$3,000 $100 by check, exchange, wire, or electronic bank transfer (other than Automatic Investment Plan, which has no established minimum).

Tax Information

The Fund’s distributions may be taxable as ordinary income or capital gain. Distributions are taxable to you for federal income tax purposes, whether or not you reinvest these amounts in additional Fund shares. Dividend distributions that you receive may also be subject to state and local income taxes.

Financial Intermediary Compensation

The Fund and its investment advisor do not pay financial intermediaries for sales of Fund shares or related services.

Vanguard Federal Money Market Fund

Investment Objective

The Fund seeks to provide current income while maintaining liquidity and a stable share price of $1.

Fees and Expenses

The following tables describe the fees and expenses you may pay if you buy and hold shares of the Fund.


Shareholder Fees
(Fees paid directly from your investment)
Sales Charge (Load) Imposed on Purchases	None
Purchase Fee	None
Sales Charge (Load) Imposed on Reinvested Dividends	None
Redemption Fee	None
Account Service Fee (for fund account balances below $10,000)	$20/year


Annual Fund Operating Expenses
(Expenses that you pay each year as a percentage of the value of your investment)
Management Expenses	0.21%
12b-1 Distribution Fee	None
Other Expenses	0.04%
Total Annual Fund Operating Expenses	0.25% ¹

Example

The following example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invest $10,000 in the Fund’s shares. This example assumes that the Fund provides a return of 5% a year and that operating expenses remain the same. The results apply whether or not you redeem your investment at the end of the given period. Although your actual costs may be higher or lower, based on these assumptions your costs would be:


1 Year	3 Years	5 Years	10 Years
$26	$80	$141	$318

Primary Investment Policies

The Fund invests primarily in high-quality, short-term money market instruments. At least 80% of the Fund’s assets are invested in securities issued by the U.S. government and its agencies and instrumentalities. Although these securities are high-quality, most of the securities held by the Fund are neither guaranteed by the U.S. Treasury nor supported by the full faith and credit of the U.S. government. To be considered high-quality, a security generally must be rated in one of the two highest credit-quality categories for short-term securities by at least two nationally recognized rating services (or by one, if only one rating service has rated the security). The Fund maintains a dollar-weighted average maturity of 90 days or less.

Primary Risks

The Fund is designed for investors with a low tolerance for risk; however, the Fund’s performance could be hurt by:

• Manager risk , which is the chance that poor security selection will cause the Fund to underperform relevant benchmarks or other funds with a similar investment objective.

Annual Total Returns

The following bar chart and table are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns compare with those of a relevant market index and a comparative benchmark . The last line item in the table is derived from data provided by Lipper Inc . Keep in mind that the Fund’s past performance does not indicate how the Fund will perform in the future. Updated performance information is available on our website at www.vanguard.com or by calling Vanguard toll-free at 800-662-744 7.

Annual Total Returns—Investor Shares ¹

1 The year-to-date return as of the most recent calendar quarter, which ended on September 30, 2009, was 0.39%.

During the periods shown in the bar chart, the highest return for a calendar quarter was 1.59% (quarter ended December 31, 2000), and the lowest return for a quarter was 0.18% (quarter ended March 31, 2004).

Average Annual Total Returns for Periods Ended December 31, 2008


	1 Year	5 Years	10 Years
Vanguard Federal Money Market Fund	2.53%	3.28%	3.42%
Comparative Benchmarks
Citigroup 3-Month U.S. Treasury Bill Index
(reflects no deduction for fees or expenses)	1.80%	3.10%	3.30%
U.S. Government Money Market Funds Average	1.71	2.68	2.85

Investment Advisor

The Vanguard Group, Inc.

Portfolio Manager

John C. Lanius, Portfolio Manager of Vanguard. He has managed the Fund since 2007.

Purchase and Sale of Fund Shares

Account Minimums

To open and maintain an account To add to an existing account

Investor Shares

$3,000 $100 by check, exchange, wire, or electronic bank transfer (other than Automatic Investment Plan, which has no established minimum).

Tax Information

Financial Intermediary Compensation

The Fund and its investment advisor do not pay financial intermediaries for sales of Fund shares or related services.

Vanguard Admiral Treasury Money Market Fund

Investment Objective

The Fund seeks to provide current income while maintaining liquidity and a stable share price of $1.

Fees and Expenses

The following tables describe the fees and expenses you may pay if you buy and hold shares of the Fund.


Shareholder Fees
(Fees paid directly from your investment)
Sales Charge (Load) Imposed on Purchases	None
Purchase Fee	None
Sales Charge (Load) Imposed on Reinvested Dividends	None
Redemption Fee	None
Account Service Fee (for fund account balances below $10,000)	$20/year


Annual Fund Operating Expenses
(Expenses that you pay each year as a percentage of the value of your investment)
Management Expenses	0.09%
12b-1 Distribution Fee	None
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.12% ¹

Example


1 Year	3 Years	5 Years	10 Years
$12	$39	$68	$154

Primary Investment Policies

The Fund invests solely in high-quality, short-term money market securities whose interest and principal payments are backed by the full faith and credit of the U.S. government. At least 80% of the Fund’s assets will always be invested in U.S. Treasury securities; the remainder of the assets may be invested in securities issued by U.S. governmental agencies. The Fund maintains a dollar-weighted average maturity of 90 days or less.

Primary Risks

The Fund is designed for investors with a low tolerance for risk; however, the Fund’s performance could be hurt by:

• Manager risk , which is the chance that poor security selection will cause the Fund to underperform relevant benchmarks or other funds with a similar investment objective.

Annual Total Returns

The following bar chart and table are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns compare with those of comparative benchmarks. The last line item in the table is derived from data provided by Lipper Inc. Keep in mind that the Fund’s past performance does not indicate how the Fund will perform in the future. Updated performance information is available on our website at www.vanguard.com or by calling Vanguard toll-free at 800-662-7447.

Annual Total Returns—Investor Shares ¹

1 The year-to-date return as of the most recent calendar quarter, which ended on September 30, 2009, was 0.24%.

During the periods shown in the bar chart, the highest return for a calendar quarter was 1.56% (quarter ended December 31, 2000), and the lowest return for a quarter was 0.21% (quarter ended March 31, 2004).

Average Annual Total Returns for Periods Ended December 31, 2008


	1 Year	5 Years	10 Years
Vanguard Admiral Treasury Money Market Fund	2.10%	3.13%	3.31%
Comparative Benchmarks
iMoneyNet Money Fund Report’s Average 100% Treasury Fund	1.13%	2.39%	2.67%
U.S. Treasury Money Market Funds Average	1.11	2.44	2.66

Investment Advisor

The Vanguard Group, Inc.

Portfolio Manager

David R. Glocke, Principal of Vanguard. He has managed the Fund since 1997.

Purchase and Sale of Fund Shares

Account Minimums

To open and maintain an account To add to an existing account

Investor Shares

$50,000 $100 by check, exchange, wire, or electronic bank transfer (other than Automatic Investment Plan, which has no established minimum).

Tax Information

Financial Intermediary Compensation

The Fund and its investment advisor do not pay financial intermediaries for sales of Fund shares or related services.

More on the Funds

This prospectus describes the primary risks you would face as a Fund shareholder. It is important to keep in mind one of the main axioms of investing: The higher the risk of losing money, the higher the potential reward. The reverse, also, is generally true: The lower the risk, the lower the potential reward. As you consider an investment in any mutual fund, you should take into account your personal tolerance for fluctuations in the securities markets. Look for this symbol throughout the prospectus. It is used to mark detailed information about the more significant risks that you would confront as a Fund shareholder. To highlight terms and concepts important to mutual fund investors, we have provided Plain Talk ^® explanations along the way. Reading the prospectus will help you decide whether a Fund is the right investment for you. We suggest that you keep this prospectus for future reference.

Share Class Overview

This prospectus offers the Funds' Investor Shares. A separate prospectus offers Institutional Shares of Vanguard Prime Money Market Fund. Institutional Shares are generally for investors who do not require special employee benefit plan services and who invest a minimum of $5 million.

The Prime Money Market Fund’s separate share classes have different expenses; as a result, their investment performances will differ.

Plain Talk About Costs of Investing

Costs are an important consideration in choosing a mutual fund. That’s because

you, as a shareholder, pay the costs of operating a fund, plus any transaction

costs incurred when the fund buys or sells securities. These costs can erode a

substantial portion of the gross income or the capital appreciation a fund

achieves. Even seemingly small differences in expenses can, over time, have a

dramatic effect on a fund’s performance.

The following sections explain the investment policies that each Fund uses in pursuit of its objective. The Fund’s board of trustees, which oversees the Fund’s management, may change investment policies in the interest of shareholders without a shareholder vote, unless those policies are designated as fundamental. The Federal Money Market Fund’s policy of investing at least 80% of its assets in securities issued by the U.S. government and its agencies and instrumentalities and the Admiral Treasury Money Market Fund’s policy of investing at least 80% of its assets in U.S. Treasury securities may be changed only upon 60 days’ notice to shareholders.

Market Exposure

Each Fund’s primary policy is to invest in very high-quality money market instruments. Also known as cash investments, these instruments are considered short-term (that is, they usually mature in 397 days or less). Each Fund maintains a dollar-weighted average maturity of 90 days or less. Vanguard Prime Money Market Fund invests more than 25% of its assets in money market instruments issued by financial services companies.

Plain Talk About Money Market Instruments

The term “money market instruments” refers to a variety of short-term, liquid

investments, usually with maturities of 397 days or less. Some common types

are Treasury bills and notes , which are securities issued by the U.S. government;

commercial paper , which are promissory notes issued by large companies or

financial firms; banker’s acceptances , which are credit instruments guaranteed by

banks; and negotiable certificates of deposit , which are issued by banks in large

denominations. Money market securities can pay fixed, variable, or floating rates

of interest.

Each Fund is subject to income risk, which is the chance that the Fund’s income will decline because of falling interest rates. A fund’s income declines when interest rates fall because the fund then must invest in lower-yielding instruments. Because each Fund’s income is based on short-term interest rates—which can fluctuate significantly over short periods—income risk is expected to be high.

A low interest rate environment could adversely affect each Fund’s return. Low interest rates could prevent the Fund from providing a positive yield and/or make it difficult to maintain a stable share price of $1.

Security Selection

The Vanguard Group, Inc. (Vanguard), advisor to the Funds, selects high-quality money market instruments. Each Fund focuses on securities of a particular class of issuer (the U.S. government, U.S. governmental agencies, or nongovernmental issuers).

Each Fund is subject to manager risk, which is the chance that poor security selection will cause the Fund to underperform relevant benchmarks or other funds with a similar investment objective.

The Funds are generally managed without regard to tax ramifications.

Plain Talk About Credit Quality

A money market instrument’s credit-quality rating is an assessment of the

issuer’s ability to pay interest and, ultimately, to repay the principal. The lower the

rating by one of the independent bond-rating agencies (for example, Moody‘s or

Standard & Poor‘s), the greater the chance—in the rating agency’s opinion—that

the issuer will default, or fail to meet its payment obligations. Direct U.S. Treasury

obligations, along with other securities backed by the “full faith and credit” of the

U.S. government, carry the highest credit ratings. All things being equal, money

market instruments with greater credit risk offer higher yields.

The Prime Money Market Fund invests in commercial paper, U.S. Treasury and agency securities, certificates of deposit, banker’s acceptances, and other money market securities. Commercial paper must be rated at least Prime-1 by Moody‘s Investors Service, Inc. or A-1 by Standard & Poor‘s. Securities that are unrated must be issued by a company with a debt rating of A3 or better by Moody‘s or A– or better by Standard & Poor‘s. The Prime Money Market Fund also invests in short-term corporate, state, and municipal obligations rated A3 or better by Moody‘s or A– or better by Standard & Poor‘s, as well as in securities that are considered suitable for the Federal Money Market Fund as described in this prospectus.

The Prime Money Market Fund is subject to industry concentration risk, which is the chance that the Fund’s performance will be significantly affected, for better or for worse, by developments in the financial services industry.

More than 25% of the Fund’s assets are invested in instruments issued by financial services companies, such as banks, insurance companies, real estate-related companies, securities firms, leasing companies, and other companies principally engaged in providing financial services to consumers and industry. These investments include, among others, bank obligations, high-quality asset-backed securities, and securities issued by the automobile finance industry. Changes in economic, regulatory, and political conditions that affect financial services companies could have a significant effect on the Fund. These conditions include changes in interest rates and defaults in payments by borrowers.

The Fund may also invest in Eurodollar and Yankee obligations, which include certificates of deposit issued in U.S. dollars by foreign banks and foreign branches of U.S. banks. Eurodollar and Yankee obligations have the same risks, such as income risk and credit risk, as those of U.S. money market instruments. Other risks of Eurodollar and Yankee obligations include the chance that a foreign government will not let U.S. dollar-denominated assets leave the country, the chance that the banks that issue Eurodollar obligations will not be subject to the same regulations as U.S.

banks, and the chance that adverse political or economic developments will affect investments in a foreign country. Before the Fund’s advisor selects a Eurodollar or Yankee obligation, however, any foreign issuer undergoes the same credit-quality analysis and tests of financial strength as those for the issuers of domestic securities.

The Federal Money Market Fund invests in securities issued by U.S. governmental agencies and instrumentalities whose interest and principal payments are neither guaranteed by the U.S.Treasury nor backed by the full faith and credit of the U.S. government. These agencies and instrumentalities include, among others, the Federal Home Loan Banks, the Federal National Mortgage Association, and the Federal Home Loan Mortgage Corporation. The Fund also may invest in securities issued by U.S. governmental agencies and instrumentalities and backed by the full faith and credit of the U.S. government, such as those issued by the Government National Mortgage Association (GNMA).

T he Admiral Treasury Money Market Fund invests solely in securities whose interest and principal payments are backed by the full faith and credit of the U.S. government. At least 80% of the Fund ’s assets will always be invested in U.S. Treasury securities. The remainder of the Fund ’s assets may include securities issued by U.S. governmental agencies such as the GNMA, the Small Business Administration, and the Federal Financing Bank.

Plain Talk About U.S. Government-Sponsored Entities

A variety of U.S. government-sponsored entities (GSEs), such as the Federal

Home Loan Mortgage Corporation (FHLMC), the Federal National Mortgage

Association (FNMA), and the Federal Home Loan Banks (FHLBs), issue debt and

mortgage-backed securities. Although GSEs may be chartered or sponsored by

acts of Congress, they are not funded by congressional appropriations. In

September of 2008, the U.S. Treasury placed FNMA and FHLMC under

conservatorship and appointed the Federal Housing Finance Agency (FHFA) to

manage their daily operations. In addition, the U.S. Treasury entered into

purchase agreements with FNMA and FHLMC to provide them with capital in

exchange for senior preferred stock. Generally, their securities are neither issued

nor guaranteed by the U.S. Treasury and are not backed by the full faith and credit

of the U.S. government. In most cases, these securities are supported only by

the credit of the GSE, standing alone. In some cases, a GSE’s securities may be

supported by the ability of the GSE to borrow from the Treasury, or may be

supported by the U.S. government in some other way. Securities issued by the

Government National Mortgage Association (GNMA), however, are backed by the

full faith and credit of the U.S. government.

Each Fund is subject, to a limited extent, to credit risk, which is the chance that the issuer of a security will fail to pay interest and principal in a timely manner, or that negative perceptions of the issuer’s ability to make such payments will cause the price of that security to decline.

The three Funds differ mainly in terms of credit risk. In absolute terms, each Fund’s credit quality is very high.

In relative terms, the Admiral Treasury Money Market Fund, which invests in securities backed by the full faith and credit of the U.S. government, offers the lowest credit risk—and generally the lowest yield—of the three Funds.

Because many of the securities included in the Federal Money Market Fund are not backed by the full faith and credit of the U.S. government, the potential credit risk and yield for the Fund are somewhat higher than for th e A dmiral Treasury Money Market Fund.

Although the credit quality of its securities is very high, the Prime Money Market Fund faces more risk because it invests in money market securities issued by private companies. It is possible that one or more of these companies may experience financial difficulties and, as a result, may fail to pay interest to the Fund or to return the Fund’s principal when repayment is due. Therefore, the Prime Money Market Fund offers the highest credit risk—and generally the highest yield—of the three Funds.

Under certain circumstances, the exposure to a single issuer could cause the Prime or the Federal Money Market Fund to fail to maintain a share price of $1.

Bear in mind that, although each Fund invests in high-quality money market instruments, the three Funds are not insured or guaranteed by the Federal Deposit Insurance Corporation or any other agency of the U.S. government.

The Prime and Federal Money Market Funds reserve the right to invest in repurchase agreements, which are subject to specific risks.

Plain Talk About Repurchase Agreements

Repurchase agreements are contracts in which a U.S. commercial bank or

securities dealer sells government securities and agrees to repurchase the

securities on a specific date (normally the next business day) at a specific price.

Repurchase agreements carry several risks. For instance, if the seller is unable to repurchase the securities as promised, a Fund may experience a loss when trying to sell the securities to another buyer. Also, if the seller becomes insolvent, a

bankruptcy court may determine that the securities do not belong to the Fund and order that the securities be used to pay off the seller’s debts. The Funds' advisor believes that these risks can be controlled through careful security and counterparty selection and monitoring.

Each Fund reserves the right to invest, to a limited extent, in adjustable-rate securities, which are types of derivatives.

Plain Talk About Derivatives

A derivative is a financial contract whose value is based on the value of a financial

asset (such as a stock, bond, or currency), a money market benchmark (such as

U.S. Treasury bill rates or the federal funds effective rate), a physical asset (such

as gold), or a market index (such as the S&P 500 Index).

An adjustable-rate security’s interest rate, as the name implies, is not set; instead, it fluctuates periodically. Generally, the security’s yield is based on a U.S. dollar-based interest-rate benchmark such as the federal funds rate, the 90-day Treasury bill rate, or the London Interbank Offered Rate (LIBOR). These securities reset their yields on a periodic basis (for example, daily, weekly, or quarterly) or upon the change in the benchmark interest rate. These yields are closely correlated to changes in money market interest rates.

The Funds will not use derivatives for speculation or for the purpose of leveraging (magnifying) investment returns.

In addition, the Prime and Federal Money Market Funds may each invest up to 10% of their net assets in illiquid securities. These are securities that a Fund may not be able to sell in the ordinary course of business.

Cash Management

Each Fund’s daily cash balance may be invested in one or more Vanguard CMT Funds, which are very low-cost money market funds. When investing in a Vanguard CMT Fund, each Fund bears its proportionate share of the at-cost expenses of the CMT Fund in which it invests.

Frequent Trading or Market-Timing

Vanguard anticipates that shareholders will purchase and sell shares of money market funds frequently because these funds are designed to offer investors a liquid investment. For this reason, the board of trustees of each Fund has determined that it is not necessary to adopt policies and procedures designed to detect and deter frequent

trading and market-timing in the money market fund shares. For information on frequent-trading limits of other Vanguard funds, please see the appropriate fund’s prospectus.

The Funds and Vanguard

Each Fund is a member of The Vanguard Group, a family of 37 investment companies with more than 160 funds holding assets of approximately $1.2 trillion. All of the funds that are members of The Vanguard Group (other than funds of funds) share in the expenses associated with administrative services and business operations, such as personnel, office space, equipment, and advertising.

Vanguard also provides marketing services to the funds. Although shareholders do not pay sales commissions or 12b-1 distribution fees, each fund (other than a fund of funds) or each share class of the fund (in the case of a fund with multiple share classes) pays its allocated share of The Vanguard Group’s marketing costs.

Plain Talk About Vanguard’s Unique Corporate Structure

The Vanguard Group is truly a mutual mutual fund company. It is owned jointly by

the funds it oversees and thus indirectly by the shareholders in those funds.

Most other mutual funds are operated by management companies that may be

owned by one person, by a private group of individuals, or by public investors

who own the management company’s stock. The management fees charged by

these companies include a profit component over and above the companies’ cost

of providing services. By contrast, Vanguard provides services to its member

funds on an at-cost basis, with no profit component, which helps to keep the

funds’ expenses low.

Investment Advisor

The Vanguard Group, Inc., P.O. Box 2600, Valley Forge, PA 19482, which began operations in 1975, serves as advisor to the Funds through its Fixed Income Group. As of August 31, 2009 , Vanguard served as advisor for approximately $1 trillion in assets. Vanguard manages the Funds on an at-cost basis, subject to the supervision and oversight of the trustees and officers of the Funds.

For the fiscal year ended August 31, 2009 , the advisory expenses represented an effective annual rate of 0.01% of each Fund’s average net assets.

For a discussion of why the board of trustees approved each Fund’s investment advisory arrangement, see the most recent annual report to shareholders covering the fiscal year ended August 31.

Vanguard’s Fixed Income Group is overseen by:

George U. Sauter , Chief Investment Officer and Managing Director of Vanguard. As Chief Investment Officer, he is responsible for the oversight of Vanguard’s Quantitative Equity and Fixed Income Groups. The investments managed by these two groups include active quantitative equity funds, equity index funds, active bond funds, index bond funds, stable value portfolios, and money market funds. Since joining Vanguard in 1987, Mr. Sauter has been a key contributor to the development of Vanguard’s stock indexing and active quantitative equity investment strategies. He received his A.B. in Economics from Dartmouth College and an M.B.A. in Finance from the University of Chicago.

Robert F. Auwaerter , Principal of Vanguard and head of Vanguard’s Fixed Income Group. He has direct oversight responsibility for all money market funds, bond funds, and stable value portfolios managed by the Fixed Income Group. He has managed investment portfolios since 1978 and has been with Vanguard since 1981. He received his B.S. in Finance from The Wharton School of the University of Pennsylvania and an M.B.A. from Northwestern University.

The managers primarily responsible for the day-to-day management of the Funds are:

David R. Glocke, Principal of Vanguard. He has worked in investment management since 1991; has managed investment portfolios for Vanguard since 1997; and manages the Prime Money Market and Admiral Treasury Money Market Funds. Education: B.S., University of Wisconsin.

John C. Lanius , Portfolio Manager. Has been with Vanguard since 1996; has worked in investment management since 1997; and manages the Federal Money Market Fund. Education: B.A., Middlebury College.

The Statement of Additional Information provides information about each portfolio manager’s compensation, other accounts under management, and ownership of shares of the Funds.

Dividends and Taxes

Fund Distributions

Each Fund distributes to shareholders virtually all of its net income (interest less expenses). The Fund’s income dividends accrue daily and are distributed monthly . You can receive your income distributions in cash, or you can have them automatically reinvested in more shares of the Fund.

Basic Tax Points

Vanguard will send you a statement each year showing the tax status of all your distributions. In addition, investors in taxable accounts should be aware of the following basic federal income tax points:

• Distributions are taxable to you whether or not you reinvest these amounts in additional Fund shares.

• Distributions declared in December—if paid to you by the end of January—are taxable as if received in December.

• Any dividend distributions that you receive are taxable to you as ordinary income.

• Any conversion between classes of shares of the same fund is a nontaxable event. By

contrast, an exchange between classes of shares of different funds is a taxable event.

Dividend distributions that you receive may be subject to state and local income taxes. Depending on your state’s rules, however, any dividends attributable to interest earned on direct obligations of the U.S. government may be exempt from state and local taxes. Vanguard will notify you each year how much, if any, of your dividends may qualify for this exemption.

This prospectus provides general tax information only. If you are investing through a tax-deferred retirement account, such as an IRA, special tax rules apply. Please consult your tax advisor for detailed information about a fund’s tax consequences for you.

General Information

Backup withholding. By law, Vanguard must withhold 28% of any taxable distributions or redemptions from your account if you do not:

Provide us with your correct taxpayer identification number;
Certify that the taxpayer identification number is correct; and
Confirm that you are not subject to backup withholding.

Similarly, Vanguard must withhold taxes from your account if the IRS instructs us to do so.

Foreign investors. Vanguard funds generally are not sold outside the United States, except to certain qualified investors. If you reside outside the United States, please consult our website at www.vanguard.com and review “Non-U.S. investors.” Foreign investors should be aware that U.S. withholding and estate taxes may apply to any investments in Vanguard funds.

Invalid addresses. If a dividend distribution check mailed to your address of record is returned as undeliverable, Vanguard will automatically reinvest all future distributions until you provide us with a valid mailing address.

Share Price

Share price, also known as net asset value , or NAV, is calculated each business day as of the close of regular trading on the New York Stock Exchange, generally 4 p.m., Eastern time. The NAV per share for the Federal and Admiral Treasury Money Market Funds is computed by dividing the total assets, minus liabilities, of the Fund by the number of Fund shares outstanding. Each share class of the Prime Money Market Fund has its own NAV, which is computed by dividing the total assets, minus liabilities, allocated to each share class by the number of Fund shares outstanding for that class. On holidays or other days when the Exchange is closed, the NAV is not calculated, and the Fund does not transact purchase or redemption requests.

The instruments held by a Vanguard money market fund are valued on the basis of amortized cost. The values of any mutual fund shares held by a fund are based on the NAVs of the shares. The values of any ETF or closed-end fund shares held by a fund are based on the market value of the shares.

Although the stable share price is not guaranteed, the NAV of Vanguard money market funds is expected to remain at $1 per share. Instruments are purchased and managed with that goal in mind.

Vanguard money market fund yields can be found weekly in the money market fund listings of most major newspapers, separate from the share price listings for other mutual funds.

Financial Highlights

The following financial highlights tables are intended to help you understand each Fund’s financial performance for the periods shown, and certain information reflects financial results for a single Fund share. The total returns in each table represent the rate that an investor would have earned or lost each period on an investment in the Fund (assuming reinvestment of all distributions). This information has been derived from the financial statements audited by PricewaterhouseCoopers LLP, an independent registered public accounting firm, whose report—along with each Fund’s financial statements—is included in the Funds' most recent annual report to shareholders. You may obtain a free copy of the latest annual or semiannual report online at www.vanguard.com or by contacting Vanguard by telephone or mail.

Plain Talk About How to Read the Financial Highlights Tables

This explanation uses the Prime Money Market Fund’s Investor Shares as an example. The Investor Shares began fiscal year 2009 with a net asset value (price) of $1.00 per share. During the year, each Investor Share earned $0.013 from investment income (interest). Shareholders received $0.013 per share in the form of dividend distributions.

The earnings ($0.013 per share) minus the distributions ($0.013 per share) resulted in a share price of $1.00 at the end of the year. For a shareholder who reinvested the distributions in the purchase of more shares, the total return was 1.31% for the year.

As of August 31, 2009 , the Investor Shares had approximately $96 billion in net assets. For the year, the expense ratio was 0.28% ($2.80 per $1,000 of net assets), and the net investment income amounted to 1.25% of average net assets.


Prime Money Market Fund Investor Shares
			Year Ended August 31,
	2009	2008	2007	2006	2005
Net Asset Value, Beginning of Period	$1.00	$1.00	$1.00	$1.00	$1.00
Investment Operations
Net Investment Income	.013	.035	.051	.043	.023
Net Realized and Unrealized Gain (Loss)
on Investments	—	—	—	—	—
Total from Investment Operations	.013	.035	.051	.043	.023
Distributions
Dividends from Net Investment Income	(.013)	(.035)	(.051)	(.043)	(.023)
Distributions from Realized Capital Gains	—	—	—	—	—
Total Distributions	(.013)	(.035)	(.051)	(.043)	(.023)
Net Asset Value, End of Period	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return ¹	1.31%	3.60%	5.23%	4.38%	2.31%
Ratios/Supplemental Data
Net Assets, End of Period (Millions)	$96,078	$92,483	$84,052	$64,578	$46,454
Ratio of Total Expenses to Average Net Assets	0.28% ²	0.23%	0.24%	0.29%	0.30%
Ratio of Net Investment Income to Average
Net Assets	1.25%	3.49%	5.10%	4.33%	2.29%

1 Total Returns do not include the account service fee that may be applicable to certain accounts with balances below $10,000.

2 Includes 0.03% of fees to participate in the Treasury Temporary Guarantee Program for Money Market Funds.


Federal Money Market Fund
			Year Ended August 31,
	2009	2008	2007	2006	2005
Net Asset Value, Beginning of Period	$1.00	$1.00	$1.00	$1.00	$1.00
Investment Operations
Net Investment Income	.011	.034	.051	.042	.022
Net Realized and Unrealized Gain (Loss)
on Investments	—	—	—	—	—
Total from Investment Operations	.011	.034	.051	.042	.022
Distributions
Dividends from Net Investment Income	(.011)	(.034)	(.051)	(.042)	(.022)
Distributions from Realized Capital Gains	—	—	—	—	—
Total Distributions	(.011)	(.034)	(.051)	(.042)	(.022)
Net Asset Value, End of Period	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return ¹	1.06%	3.46%	5.17%	4.31%	2.26%
Ratios/Supplemental Data
Net Assets, End of Period (Millions)	$9,386	$8,982	$7,672	$6,360	$5,507
Ratio of Total Expenses to Average Net Assets	0.27% ²	0.23%	0.24%	0.29%	0.30%
Ratio of Net Investment Income to Average
Net Assets	1.03%	3.33%	5.05%	4.25%	2.23%

1 Total Returns do not include the account service fee that may be applicable to certain accounts with balances below $10,000.

2 Includes 0.02% of fees to participate in the Treasury Temporary Guarantee Program for Money Market Funds.


Admiral Treasury Money Market Fund
			Year Ended August 31,
	2009	2008	2007	2006	2005
Net Asset Value, Beginning of Period	$1.00	$1.00	$1.00	$1.00	$1.00
Investment Operations
Net Investment Income	.007	.030	.049	.041	.023
Net Realized and Unrealized Gain (Loss)
on Investments	—	—	—	—	—
Total from Investment Operations	.007	.030	.049	.041	.023
Distributions
Dividends from Net Investment Income	(.007)	(.030)	(.049)	(.041)	(.023)
Distributions from Realized Capital Gains	—	—	—	—	—
Total Distributions	(.007)	(.030)	(.049)	(.041)	(.023)
Net Asset Value, End of Period	$1.00	$1.00	$1.00	$1.00	$1.00
Total Return	0.70%	3.08%	5.02%	4.22%	2.29%
Ratios/Supplemental Data
Net Assets, End of Period (Millions)	$25,435 $23,289 $20,064			$15,982	$13,838
Ratio of Total Expenses to Average Net Assets	0.15% ¹	0.10%	0.10%	0.13%	0.13%
Ratio of Net Investment Income to Average
Net Assets	0.74%	2.98%	4.90%	4.15%	2.27%

1 Includes 0.03% of fees to participate in the Treasury Temporary Guarantee Program for Money Market Funds.

Investing With Vanguard

This section of the prospectus explains the basics of doing business with Vanguard. Be sure to carefully read each topic that pertains to your relationship with Vanguard. Vanguard reserves the right to change the following policies, without notice to shareholders. Please call or check online for current information.

Each fund you hold in an account is a separate “fund account.” For example, if you hold three funds in a nonretirement account titled in your own name, two funds in a nonretirement account titled jointly with your spouse, and one fund in an individual retirement account, you have six fund accounts—and this is true even if you hold the same fund in multiple accounts.

Purchasing Shares

Vanguard reserves the right, without notice, to increase or decrease the minimum amount required to open, convert shares to, or maintain a fund account, or to add to an existing fund account.

Investment minimums may differ for certain categories of investors.

Account Minimums

To open and maintain an account. For the Admiral Treasury Money Market Fund only: $50,000. For the other two Funds: $3,000.

Add to an existing account. $100 by check, exchange, wire, or electronic bank transfer (other than Automatic Investment Plan, which has no established minimum).

How to Initiate a Purchase Request

Be sure to check Exchanging Shares and Other Rules You Should Know before placing your purchase request.

Online. You may open certain types of accounts, request a purchase of shares, and request an exchange (the purchase of shares of one Vanguard fund using the proceeds of a simultaneous redemption from another Vanguard fund) through our website at www.vanguard.com if you are a registered user.

By telephone. You may call Vanguard to begin the account registration process or request that the account-opening forms be sent to you. You may also call Vanguard to request a purchase of shares. See Contacting Vanguard .

By mail. You may send Vanguard your account registration form and check to open a new fund account. To add to an existing fund account, you may send your check with an Invest-by-Mail form (from your account statement), with a deposit slip (available online), or with a written request. You may also send a written request to Vanguard to make an exchange. For a list of Vanguard addresses, see Contacting Vanguard .

How to Pay for a Purchase

By electronic bank transfer. You may purchase shares of a Vanguard fund through an electronic transfer of money from a bank account. To establish the electronic bank transfer option on an account, you must designate the bank account online, complete a special form, or fill out the appropriate section of your account registration form. After the option is set up on your account, you can purchase shares by electronic bank transfer on a regular schedule (Automatic Investment Plan) or from time to time. Your purchase request can be initiated online (if you are a registered user of Vanguard.com ), by telephone, or by mail.

By wire. Wiring instructions vary for different types of purchases. Please call Vanguard for instructions and policies on purchasing shares by wire. See Contacting Vanguard.

By check. You may send a check to make initial or additional purchases to your fund account. Also see How to Initiate a Purchase Request: By mail . Make your check payable to Vanguard and include the appropriate fund number (e.g., Vanguard—xx). For a list of Fund numbers (for Funds in this prospectus), see Additional Information .

By exchange. You may purchase shares of a Vanguard fund using the proceeds from the simultaneous redemption of shares of another Vanguard fund. You may initiate an exchange online (if you are a registered user of Vanguard.com ), by telephone, or by mail. See Exchanging Shares .

Trade Date

The trade date for any purchase request received in good order will depend on the day and time Vanguard receives your request, the manner in which you are paying, and the type of fund you are purchasing. Your purchase will be executed using the NAV as calculated on the trade date. NAVs are calculated only on days that the New York Stock Exchange (NYSE) is open for regular trading (a business day).

For purchases by check into all funds other than money market funds, and for purchases by exchange or wire into all funds: If the purchase request is received by Vanguard on a business day before the close of regular trading on the NYSE (generally 4 p.m., Eastern time), the trade date will be the same day. If the purchase request is received on a business day after the close of regular trading on the NYSE, or on a nonbusiness day, the trade date will be the next business day.

For purchases by check into money market funds: If the purchase request is received by Vanguard on a business day before the close of regular trading on the NYSE (generally 4 p.m., Eastern time), the trade date will be the next business day. If the purchase request is received on a business day after the close of regular trading on the NYSE, or on a nonbusiness day, the trade date will be the second business day following the day Vanguard receives the purchase request. Because money market instruments must be purchased with federal funds and it takes a money market

mutual fund one business day to convert check proceeds into federal funds, the trade date will be one business day later than for other funds.

For purchases by electronic bank transfer using an Automatic Investment Plan : Your trade date generally will be one business day before the date you designated for withdrawal from your bank account.

For purchases by electronic bank transfer not using an Automatic Investment Plan: If the purchase request is received by Vanguard on a business day before 10 p.m., Eastern time, the trade date generally will be the next business day. If the purchase request is received on a business day after 10 p.m., Eastern time, or on a nonbusiness day, the trade date will be the second business day following the day Vanguard receives the request.

If your purchase request is not accurate and complete, it may be rejected. See Other Rules You Should Know—Good Order .

For further information about purchase transactions, consult our website at www.vanguard.com or see Contacting Vanguard .

Earning Dividends

You generally begin earning dividends on the business day following your trade date. When buying money market fund shares through a federal funds wire, however, you can begin earning dividends immediately by making a purchase request by telephone to Vanguard before 10:45 a.m., Eastern time (2 p.m., Eastern time, for Vanguard Prime Money Market Fund).

Other Purchase Rules You Should Know

Check purchases. All purchase checks must be written in U.S. dollars and must be drawn on a U.S. bank. Vanguard does not accept cash, traveler’s checks, or money orders. In addition, Vanguard may refuse “starter checks” and checks that are not made payable to Vanguard.

New accounts. We are required by law to obtain from you certain personal information that we will use to verify your identity. If you do not provide the information, we may not be able to open your account. If we are unable to verify your identity, Vanguard reserves the right, without notice, to close your account or take such other steps as we deem reasonable.

Refused or rejected purchase requests. Vanguard reserves the right to stop selling fund shares or to reject any purchase request at any time and without notice, including, but not limited to, purchases requested by exchange from another Vanguard fund. This also includes the right to reject any purchase request because of a history of frequent

trading by the investor or because the purchase may negatively affect a fund’s operation or performance.

Large purchases. Please call Vanguard before attempting to invest a large dollar amount.

No cancellations. Vanguard will not accept your request to cancel any purchase request once processing has begun. Please be careful when placing a purchase request.

Converting Shares

When a conversion occurs, you receive shares of one class in place of shares of another class of the same fund. At the time of conversion, the dollar value of the “new” shares you receive equals the dollar value of the “old” shares that were converted. In other words, the conversion has no effect on the value of your investment in the fund at the time of the conversion. However, the number of shares you own after the conversion may be greater than or less than the number of shares you owned before the conversion, depending on the net asset values of the two share classes.

A conversion between share classes of the same fund is a nontaxable event.

Trade Date

The trade date for any conversion request received in good order will depend on the day and time Vanguard receives your request. Your conversion will be executed using the NAVs of the different share classes on the trade date. NAVs are calculated only on days that the NYSE is open for regular trading (a business day).

For a conversion request received by Vanguard on a business day before the close of regular trading on the NYSE (generally 4 p.m., Eastern time), the trade date will be the same day. For a conversion request received on a business day after the close of regular trading on the NYSE, or on a nonbusiness day, the trade date will be the next business day. See Other Rules You Should Know.

Conversions to Institutional Shares

You are eligible for a self-directed conversion from another share class to Institutional Shares of the same Fund (if available), provided that your account meets all Institutional Shares’ eligibility requirements. Registered users of our website, www.vanguard.com , may request a conversion online, or you may contact Vanguard by telephone or by mail to request this transaction. Accounts that qualify for Institutional Shares will not be automatically converted.

Mandatory Conversions to Investor Shares

If an account no longer meets the balance requirements for Institutional Shares, Vanguard may automatically convert the shares in the account to Investor Shares. A decline in the account balance because of market movement may result in such a conversion. Vanguard will notify the investor in writing before any mandatory conversion occurs.

Redeeming Shares

How to Initiate a Redemption Request

Be sure to check Exchanging Shares and Other Rules You Should Know before initiating your request.

Online. You may request a redemption of shares and request an exchange (using the proceeds from the redemption of shares of one Vanguard fund to simultaneously purchase shares of a different Vanguard fund) through our website at www.vanguard.com if you are a registered user.

By telephone. You may call Vanguard to request a redemption of shares. See

Contacting Vanguard .

By mail. You may send a written request to Vanguard to redeem from a fund account or to make an exchange. See Contacting Vanguard .

By writing a check. If you’ve established the checkwriting service on your account, you can redeem shares by writing a check for $250 or more.

How to Receive Redemption Proceeds

By electronic bank transfer. You may have the proceeds of a fund redemption sent directly to a designated bank account. To establish the electronic bank transfer option on an account, you must designate a bank account online, complete a special form, or fill out the appropriate section of your account registration form. After the option is set up on your account, you can redeem shares by electronic bank transfer on a regular schedule (Automatic Withdrawal Plan) or from time to time. Your redemption request can be initiated online, by telephone, or by mail.

By wire. When redeeming from a money market fund or a bond fund, you may instruct Vanguard to wire your redemption proceeds ($1,000 minimum) to a previously designated bank account. Wire redemptions generally are not available for Vanguard’s balanced or stock funds. The wire redemption option is not automatic ; you must designate a bank account online, complete a special form, or fill out the appropriate section of your account registration form. Vanguard generally charges a $5 fee for wire redemptions under $5,000.

By exchange. You may have the proceeds of a Vanguard fund redemption invested directly in shares of another Vanguard fund. You may initiate an exchange online (if you are a registered user of Vanguard.com ), by telephone, or by mail.

By check. If you have not chosen another redemption method, Vanguard will mail you a redemption check, generally payable to all registered account owners, normally within two business days of your trade date.

Trade Date

The trade date for any redemption request received in good order will depend on the day and time Vanguard receives your request and the manner in which you are redeeming. Your redemption will be executed using the NAV as calculated on the trade date. NAVs are calculated only on days that the NYSE is open for regular trading (a business day).

For redemptions by check , exchange , or wire : If the redemption request is received by Vanguard on a business day before the close of regular trading on the NYSE (generally 4 p.m., Eastern time), the trade date will be the same day. If the redemption request is received on a business day after the close of regular trading on the NYSE, or on a nonbusiness day, the trade date will be the next business day.

• Note on timing of wire redemptions from money market funds: For telephone requests received by Vanguard on a business day before 10:45 a.m., Eastern time (2 p.m., Eastern time, for Vanguard Prime Money Market Fund), the redemption proceeds generally will leave Vanguard by the close of business the same day. For telephone requests received by Vanguard on a business day after those cut-off times, or on a nonbusiness day, and for all requests other than by telephone, the redemption proceeds generally will leave Vanguard by the close of business on the next business day.

• Note on timing of wire redemptions from bond funds: For requests received by Vanguard on a business day before the close of regular trading on the NYSE (generally 4 p.m., Eastern time), the redemption proceeds generally will leave Vanguard by the close of business on the next business day. For requests received by Vanguard on a business day after the close of regular trading on the NYSE, or on a nonbusiness day, the redemption proceeds generally will leave Vanguard by the close of business on the second business day after Vanguard receives the request.

For redemptions by electronic bank transfer using an Automatic Withdrawal Plan : Your trade date generally will be the date you designated for withdrawal of funds (redemption of shares) from your Vanguard account. Proceeds of redeemed shares generally will be credited to your designated bank account two business days after your trade date. If the date you designated for withdrawal of funds from your

Vanguard account falls on a weekend, holiday, or other nonbusiness day, your trade date will be the previous business day.

For redemptions by electronic bank transfer not using an Automatic Withdrawal Plan: If the redemption request is received by Vanguard on a business day before the close of regular trading on the NYSE (generally 4 p.m., Eastern time), the trade date will be the same day. If the redemption request is received on a business day after the close of regular trading on the NYSE, or on a nonbusiness day, the trade date will be the next business day.

If your redemption request is not accurate and complete, it may be rejected. If we are unable to send your redemption proceeds by wire or electronic bank transfer because the receiving institution rejects the transfer, Vanguard will make additional efforts to complete your transaction. If Vanguard is still unable to complete the transaction, we may use your proceeds to purchase new shares of the Fund in which you sold shares for the purpose of the wire or electronic bank transfer transaction. See Other Rules You Should Know—Good Order .

For further information about redemption transactions, consult our website at www.vanguard.com or see Contacting Vanguard .

Earning Dividends

You generally will continue earning dividends until the first business day following your trade date. Generally, there are two exceptions to this rule: (1) If you redeem shares by writing a check against your account, the shares will stop earning dividends on the day that your check posts to your account; and (2) For money market funds, if you redeem shares with a same-day wire request before 10:45 a.m., Eastern time (2 p.m., Eastern time for Vanguard Prime Money Market Fund), the shares will stop earning dividends that same day.

Other Redemption Rules You Should Know

Documentation for certain accounts. Special documentation may be required to redeem from certain types of accounts, such as trust, corporate, nonprofit, or retirement accounts. Please call us before attempting to redeem from these types of accounts.

Potentially disruptive redemptions. Vanguard reserves the right to pay all or part of a redemption in kind—that is, in the form of securities—if we reasonably believe that a cash redemption would negatively affect the fund’s operation or performance or that the shareholder may be engaged in market-timing or frequent trading. Under these circumstances, Vanguard also reserves the right to delay payment of the redemption proceeds for up to seven calendar days. By calling us before you attempt to redeem a large dollar amount, you may avoid in-kind or delayed payment of your redemption.

Recently purchased shares. Although you can redeem shares at any time, proceeds may not be made available to you until the fund collects payment for your purchase. This may take up to ten calendar days for shares purchased by check or by electronic bank transfer. If you have written a check on a fund with checkwriting privileges, that check may be rejected if your fund account does not have a sufficient available balance.

Share certificates. If you hold shares in certificates, those shares cannot be redeemed, exchanged, or converted until you return the certificates (unsigned) to Vanguard by registered mail. For the correct address, see Contacting Vanguard .

Address change. If you change your address online or by telephone, there may be a 15-day restriction on your ability to request redemptions online and by telephone. You can request a redemption in writing at any time. Confirmations of address changes are sent to both the old and new addresses.

Payment to a different person or address. At your request, we can make your redemption check payable, or wire your redemption proceeds, to a different person or send it to a different address. However, this generally requires the written consent of all registered account owners and may require a signature guarantee. You may obtain a signature guarantee from some commercial or savings banks, credit unions, trust companies, or member firms of a U.S. stock exchange. A notary public cannot provide a signature guarantee.

No cancellations. Vanguard will not accept your request to cancel any redemption request once processing has begun. Please be careful when placing a redemption request.

Emergency circumstances. Vanguard funds can postpone payment of redemption proceeds for up to seven calendar days. In addition, Vanguard funds can suspend redemptions and/or postpone payments of redemption proceeds beyond seven calendar days at times when the NYSE is closed or during emergency circumstances, as determined by the SEC.

Exchanging Shares

An exchange occurs when you use the proceeds from the redemption of shares of one Vanguard fund to simultaneously purchase shares of a different Vanguard fund. You can make exchange requests online (if you are a registered user of Vanguard.com ), by telephone, or by mail. See Purchasing Shares and Redeeming Shares .

If the NYSE is open for regular trading (generally until 4 p.m., Eastern time, on a business day) at the time an exchange request is received in good order, the trade date generally will be the same day. See Other Rules You Should Know—Good Order for additional information on all transaction requests.

Vanguard will not accept your request to cancel any exchange request once processing has begun. Please be careful when placing an exchange request.

Please note that Vanguard reserves the right, without notice, to revise or terminate the exchange privilege, limit the amount of any exchange, or reject an exchange, at any time, for any reason.

Other Rules You Should Know

Prospectus and Shareholder Report Mailings

Vanguard attempts to eliminate the unnecessary expense of duplicate mailings by sending just one prospectus and/or report when two or more shareholders have the same last name and address. You may request individual prospectuses and reports by contacting our Client Services Department in writing, by telephone, or by e-mail.

Vanguard.com

Registration. If you are a registered user of Vanguard.com, you can use your personal computer to review your account holdings; to buy, sell, or exchange shares of most Vanguard funds; and to perform most other transactions. You must register for this service online.

Electronic delivery. Vanguard can deliver your account statements, transaction confirmations, and fund financial reports electronically. If you are a registered user of Vanguard.com , you can consent to the electronic delivery of these documents by logging on and changing your mailing preference under “Account Profile.” You can revoke your electronic consent at any time online, and we will begin to send paper copies of these documents within 30 days of receiving your revocation.

Telephone Transactions

Automatic. When we set up your account, we’ll automatically enable you to do business with us by telephone, unless you instruct us otherwise in writing.

Tele-Account ^® . To conduct account transactions through Vanguard’s automated telephone service, you must first obtain a Personal Identification Number (PIN). Call Tele-Account at 800-662-6273 to obtain a PIN, and allow seven days after requesting the PIN before using this service.

Proof of a caller’s authority. We reserve the right to refuse a telephone request if the caller is unable to provide the requested information or if we reasonably believe that the caller is not an individual authorized to act on the account. Before we allow a caller to act on an account, we may request the following information:

• Authorization to act on the account (as the account owner or by legal documentation or other means).

Account registration and address.
Fund name and account number, if applicable.
Other information relating to the caller, the account owner, or the account.

Good Order

We reserve the right to reject any transaction instructions that are not in “good order.” Good order generally means that your instructions include:

The fund name and account number.
The amount of the transaction (stated in dollars, shares, or percentage).

Written instructions also must include:

Signatures of all registered owners.
Signature guarantees, if required for the type of transaction. (Call Vanguard for

specific signature-guarantee requirements.)

• Any supporting documentation that may be required.

The requirements vary among types of accounts and transactions.

Vanguard reserves the right, without notice, to revise the requirements for good order.

Future Trade-Date Requests

Vanguard does not accept requests to hold a purchase, conversion, redemption, or exchange transaction for a future date. All such requests will receive trade dates as previously described in Purchasing Shares , Converting Shares , and Redeeming Shares . Vanguard reserves the right to return future-dated purchase checks.

Accounts With More Than One Owner

If an account has more than one owner or authorized person, Vanguard will accept telephone or online instructions from any one owner or authorized person.

Responsibility for Fraud

Vanguard will not be responsible for any account losses because of fraud if we reasonably believe that the person transacting business on an account is authorized to do so. Please take precautions to protect yourself from fraud. Keep your account information private, and immediately review any account statements that we provide to you. It is important that you contact Vanguard immediately about any transactions or changes to your account that you believe to be unauthorized.

Uncashed Checks

Please cash your distribution or redemption checks promptly. Vanguard will not pay interest on uncashed checks.

Unusual Circumstances

If you experience difficulty contacting Vanguard online, by telephone, or by Tele-Account, you can send us your transaction request by regular or express mail. See

Contacting Vanguard for addresses.

Investing With Vanguard Through Other Firms

You may purchase or sell shares of most Vanguard funds through a financial intermediary, such as a bank, broker, or investment advisor. Please consult your financial intermediary to determine which, if any, shares are available through that firm and to learn about other rules that may apply.

Account Service Fee

For most shareholders, Vanguard charges a $20 account service fee on all fund accounts that have a balance below $10,000 for any reason, including market fluctuation. The account service fee applies to both retirement and nonretirement fund accounts and will be assessed on fund accounts in all Vanguard funds, regardless of a fund’s minimum investment amount. The fee, which will be collected by redeeming fund shares in the amount of $20, will be deducted from a fund account only once per calendar year.

If you register on Vanguard.com and elect to receive electronic delivery of statements, reports, and other materials for all of your fund accounts, the account service fee for balances below $10,000 will not be charged, so long as that election remains in effect.

The account service fee also does not apply to the following:

• Money market sweep accounts owned in connection with a Vanguard Brokerage Services ^® account.

Accounts held through intermediaries.
Accounts held by Voyager, Voyager Select, and Flagship members. Membership is

based on total household assets held at Vanguard, with a minimum of $100,000 to qualify for Vanguard Voyager Services ^® , $500,000 for Vanguard Voyager Select Services ^® , and $1 million for Vanguard Flagship Services ^® . Vanguard determines membership by aggregating assets of all eligible accounts held by the investor and immediate family members who reside at the same address. Aggregate assets include investments in Vanguard mutual funds, Vanguard ETFs ™ , annuities through Vanguard,

the Vanguard 529 Plan, certain small-business accounts, and employer-sponsored retirement plans for which Vanguard provides recordkeeping services.

• Participant accounts in employer-sponsored defined contribution plans.* Please consult your enrollment materials for the rules that apply to your account.

Section 529 college savings plans.
The following Vanguard fund accounts have alternative fee structures: SIMPLE IRAs,

certain Section 403(b)(7) accounts, Vanguard Retirement Investment Program pooled plans, and Vanguard Retirement Plans for which Vanguard Fiduciary Trust Company serves as trustee.

Low-Balance Accounts

Each Fund reserves the right to liquidate a fund account whose balance falls below the minimum initial investment for any reason, including market fluctuation. This policy applies to nonretirement fund accounts and accounts that are held through intermediaries.

Right to Change Policies

In addition to the rights expressly stated elsewhere in this prospectus, Vanguard reserves the right, without notice, to (1) alter, add, or discontinue any conditions of purchase (including eligibility requirements), redemption, exchange, conversion, service, or privilege at any time; (2) accept initial purchases by telephone; (3) freeze any account and/or suspend account services if Vanguard has received reasonable notice of a dispute regarding the assets in an account, including notice of a dispute between the registered or beneficial account owners, or if we reasonably believe a fraudulent transaction may occur or has occurred; (4) temporarily freeze any account and/or suspend account services upon initial notification to Vanguard of the death of the shareholder until Vanguard receives required documentation in good order; (5) alter, impose, discontinue, or waive any redemption fee, account service fee, or other fees charged to a group of shareholders; and (6) redeem an account or suspend account privileges, without the owner’s permission to do so, in cases of threatening conduct or activity Vanguard believes to be suspicious, fraudulent, or illegal. Changes may affect any or all investors. These actions will be taken when, at the sole discretion of Vanguard management, we reasonably believe they are deemed to be in the best interest of a fund.

Share Classes

Vanguard reserves the right, without notice, to change the eligibility requirements of its share classes, including the types of clients who are eligible to purchase each share class.

Fund and Account Updates

Confirmation Statements

We will send (or provide online, whichever you prefer) a confirmation of your trade date and the amount of your transaction when you buy, sell, exchange, or convert shares. However, we will not send confirmations reflecting only checkwriting redemptions or the reinvestment of dividend or capital gains distributions. For any month in which you had a checkwriting redemption, a Checkwriting Activity Statement will be sent to you itemizing the checkwriting redemptions for that month. Promptly review each confirmation statement that we provide to you by mail or online. It is important that you contact Vanguard immediately with any questions you may have about any transaction reflected on a confirmation statement, or Vanguard will consider the transaction properly processed.

Portfolio Summaries

We will send (or provide online, whichever you prefer) quarterly portfolio summaries to help you keep track of your accounts throughout the year. Each summary shows the market value of your account at the close of the statement period, as well as all distributions, purchases, redemptions, exchanges, transfers, and conversions for the current calendar year. Promptly review each summary that we provide to you by mail or online. It is important that you contact Vanguard immediately with any questions you may have about any transaction reflected on the summary, or Vanguard will consider the transaction properly processed.

Tax Statements

For most accounts, we will send annual tax statements to assist you in preparing your income tax returns. These statements, which are generally mailed in January, will report the previous year’s dividends, proceeds from the sale of shares from taxable accounts, and distributions from IRAs and other retirement plans. Registered users can view these statements online.

Average-Cost Review Statements

For most taxable accounts, average-cost review statements will accompany annual Forms 1099 - B. These statements show the average cost of shares that you redeemed during the previous calendar year, using the average-cost single-category method, which is one of the methods established by the IRS.

Annual and Semiannual Reports

We will send (or provide online, whichever you prefer) financial reports about Vanguard Money Market Funds twice a year, in April and October. These

comprehensive reports include overviews of the financial markets and provide the following specific Fund information:

Performance assessments and comparisons with industry benchmarks.
Reports from the advisor.
Financial statements with listings of Fund holdings.

Portfolio Holdings

We generally post on our website at www.vanguard.com , in the Portfolio section of each Fund’s Portfolio & Management page, a detailed list of the securities held by the Fund as of the end of the most recent month. This list is generally updated approximately 2 business days after the end of the month. Vanguard may exclude any portion of these portfolio holdings from publication when deemed in the best interest of the Fund. Please consult the Funds' Statement of Additional Information or our website for a description of the policies and procedures that govern disclosure of the Funds' portfolio holdings.


Contacting Vanguard


Web
Vanguard.com	For the most complete source of Vanguard news
24 hours a day, 7 days a week	For fund, account, and service information
	For most account transactions
	For literature requests

Phone
Vanguard Tele-Account ^® 800-662-6273	For automated fund and account information
(ON-BOARD)	For exchange transactions (subject to limitations)
	Toll-free, 24 hours a day, 7 days a week
Investor Information 800-662-7447 (SHIP) For fund and service information
(Text telephone for people with hearing	For literature requests
impairment at 800-749-7273)	Business hours only: Monday–Friday, 8 a.m. to 10 p.m.,
	Eastern time; Saturday, 9 a.m. to 4 p.m., Eastern time
Client Services 800-662-2739 (CREW)	For account information
(Text telephone for people with hearing	For most account transactions
impairment at 800-749-7273)	Business hours only: Monday–Friday, 8 a.m. to 10 p.m.,
	Eastern time; Saturday, 9 a.m. to 4 p.m., Eastern time
Institutional Division	For information and services for large institutional investors
888-809-8102	Business hours only: Monday–Friday, 8:30 a.m. to 9 p.m.,
	Eastern time
Intermediary Sales Support	For information and services for financial intermediaries
800-997-2798	including broker-dealers, trust institutions, insurance
	companies, and financial advisors
	Business hours only: Monday–Friday, 8:30 a.m. to 7 p.m.,
	Eastern time

Vanguard Addresses

Please be sure to use the correct address, depending on your method of delivery. Use of an incorrect address could delay the processing of your transaction.


Regular Mail (Individuals)	The Vanguard Group P.O. Box 1110 Valley Forge, PA 19482-1110
Regular Mail (Institutions)	The Vanguard Group P.O. Box 2900 Valley Forge, PA 19482-2900
Registered, Express, or Overnight	The Vanguard Group 455 Devon Park Drive Wayne, PA 19087-1815


Additional Information

	Inception	Suitable	Newspaper	Vanguard	CUSIP
	Date	for IRAs	Abbreviation	Fund Number	Number
Prime Money Market Fund	6/4/1975	Yes	VangPr	30	922906201
Federal Money Market Fund	7/13/1981	Yes	VangFdl	33	922906300
Admiral Treasury Money	12/14/1992	Yes VangAdmUST		11	921932109
Market Fund

Glossary of Investment Terms

Dividend Distribution. Payment to mutual fund shareholders of income from interest or dividends generated by a fund’s investments.

Expense Ratio. The percentage of a fund’s average net assets used to pay its expenses during a fiscal year. The expense ratio includes management expenses—such as advisory fees, account maintenance, reporting, accounting, legal, and other administrative expenses—and any 12b-1 distribution fees. It does not include the transaction costs of buying and selling portfolio securities.

Inception Date. The date on which the assets of a fund (or one of its share classes) are first invested in accordance with the fund’s investment objective. For funds with a subscription period, the inception date is the day after that period ends. Investment performance is measured from the inception date.

Money Market Instruments. Short-term, liquid investments (usually with a maturity of 397 days or less) that include U.S. Treasury bills and notes, bank certificates of deposit (CDs), repurchase agreements, commercial paper, and banker’s acceptances.

Mutual Fund. An investment company that pools the money of many people and invests it in a variety of securities in an effort to achieve a specific objective over time.

Principal. The face value of a debt instrument or the amount of money put into an investment.

Securities. Stocks, bonds, money market instruments, and other investment vehicles.

Total Return. A percentage change, over a specified time period, in a mutual fund’s net asset value, assuming the reinvestment of all distributions of dividends and capital gains.

Volatility. The fluctuations in value of a mutual fund or other security. The greater a fund’s volatility, the wider the fluctuations in its returns.

Yield. Income (interest or dividends) earned by an investment, expressed as a percentage of the investment’s price.

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P.O. Box 2600
Valley Forge, PA 19482-2600

Connect with Vanguard ^® > www.vanguard.com

For More Information

If you would like more information about Vanguard Money Market Funds, the following documents are available free upon request:

Annual/Semiannual Reports to Shareholders

Additional information about the Funds’ investments is available in the Funds’ annual and semiannual reports to shareholders. In the annual report, you will find a discussion of the market conditions and investment policies that significantly affected the Funds’ performance during their last fiscal year.

Statement of Additional Information (SAI)

The SAI provides more detailed information about the Funds.

The current annual and semiannual reports and the SAI are incorporated by reference into (and are thus legally a part of) this prospectus.

To receive a free copy of the latest annual or semiannual report or the SAI, or to request additional information about the Funds or other Vanguard funds, please visit www.vanguard.com or contact us as follows:

The Vanguard Group

Investor Information Department P.O. Box 2600 Valley Forge, PA 19482-2600 Telephone: 800-662-7447 (SHIP)

Text telephone for people with hearing impairment: 800-749-7273

If you are a current Vanguard shareholder and would like information about your account, account transactions, and/or account statements, please call:

Client Services Department Telephone: 800-662-2739 (CREW)

Text telephone for people with hearing impairment: 800-749-7273

Information Provided by the Securities and Exchange Commission (SEC)

You can review and copy information about the Funds (including the SAI) at the SEC’s Public Reference Room in Washington, DC. To find out more about this public service, call the SEC at 202-551-8090. Reports and other information about the Funds are also available in the EDGAR database on the SEC’s Internet site at www.sec.gov, or you can receive copies of this information, for a fee, by electronic request at the following e-mail address: publicinfo@sec.gov, or by writing the Public Reference Section, Securities and Exchange Commission, Washington, DC 20549-1520.

Funds’ Investment Company Act file number: Prime and Federal Money Market Funds: 811-2554; Admiral Treasury Money Market Fund: 811-7043

Vanguard Marketing Corporation, Distributor.

P030 122009

Vanguard Money Market Funds Prospectus

December 23, 2009

Investor Shares for Participants

Vanguard Prime Money Market Fund (VMMXX)

Vanguard Federal Money Market Fund (VMFXX)

Vanguard Admiral™ Treasury Money Market Fund (VUSXX)

This prospectus contains financial data for the Funds through the fiscal year ended August 31, 2009 .

The Securities and Exchange Commission has not approved or disapproved these securities or passed upon the adequacy of this prospectus. Any representation to the contrary is a criminal offense.


Contents


Vanguard Fund Summaries		Financial Highlights	22
Prime Money Market Fund	1	Investing With Vanguard	26
Federal Money Market Fund	5	Accessing Fund Information by Computer	28
Admiral Treasury Money Market Fund	9	Glossary of Investment Terms	29
More on the Funds	13
The Funds and Vanguard	19
Investment Advisor	19
Dividends and Taxes	20
Share Price	21

Vanguard Prime Money Market Fund

Investment Objective

The Fund seeks to provide current income while maintaining liquidity and a stable share price of $1.

Fees and Expenses

The following tables describe the fees and expenses you may pay if you buy and hold Investor Shares of the Fund.


Shareholder Fees
(Fees paid directly from your investment)
Sales Charge (Load) Imposed on Purchases	None
Purchase Fee	None
Sales Charge (Load) Imposed on Reinvested Dividends	None
Redemption Fee	None


Annual Fund Operating Expenses
(Expenses that you pay each year as a percentage of the value of your investment)
Management Expenses	0.21%
12b-1 Distribution Fee	None
Other Expenses	0.04%
Total Annual Fund Operating Expenses	0.25% ¹

Example


1 Year	3 Years	5 Years	10 Years
$26	$80	$141	$318

Primary Investment Policies

Primary Risks

The Fund is designed for investors with a low tolerance for risk; however, the Fund’s performance could be hurt by:

• Manager risk , which is the chance that poor security selection will cause the Fund to underperform relevant benchmarks or other funds with a similar investment objective.

Annual Total Returns

The following bar chart and table are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund’s Investor Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Fund’s Investor Shares compare with those of a relevant market index and a comparative benchmark . The last line item in the table is derived from data provided by Lipper Inc . Keep in mind that the Fund’s past performance does not indicate how the Fund will perform in the future. Updated performance information is available on our website at www.vanguard.com or by calling Vanguard toll-free at 800-662-744 7.

Annual Total Returns—Investor Shares ¹

1 The year-to-date return as of the most recent calendar quarter, which ended on September 30, 2009, was 0.50%.

Average Annual Total Returns for Periods Ended December 31, 2008


	1 Year	5 Years	10 Years
Vanguard Prime Money Market Fund Investor Shares	2.77%	3.37%	3.48%
Comparative Benchmarks
Citigroup 3-Month U.S. Treasury Bill Index
(reflects no deduction for fees or expenses)	1.80%	3.10%	3.30%
Money Market Funds Average	2.04	2.73	2.86

Investment Advisor

The Vanguard Group, Inc.

Portfolio Manager

David R. Glocke, Principal of Vanguard. He has managed the Fund since 2003.

Tax Information

The Fund’s distributions will be reinvested in additional Fund shares and accumulate on a tax-deferred basis if you are investing through an employer-sponsored retirement or savings plan. You will not owe taxes on these distributions until you begin withdrawals from the plan. You should consult your plan administrator, your plan’s Summary Plan Description, or your tax advisor about the tax consequences of plan withdrawals.

Financial Intermediary Compensation

The Fund and its investment advisor do not pay financial intermediaries for sales of Fund shares or related services.

Vanguard Federal Money Market Fund

Investment Objective

The Fund seeks to provide current income while maintaining liquidity and a stable share price of $1.

Fees and Expenses

The following tables describe the fees and expenses you may pay if you buy and hold shares of the Fund.


Shareholder Fees
(Fees paid directly from your investment)
Sales Charge (Load) Imposed on Purchases	None
Purchase Fee	None
Sales Charge (Load) Imposed on Reinvested Dividends	None
Redemption Fee	None


Annual Fund Operating Expenses
(Expenses that you pay each year as a percentage of the value of your investment)
Management Expenses	0.21%
12b-1 Distribution Fee	None
Other Expenses	0.04%
Total Annual Fund Operating Expenses	0.25% ¹

Example


1 Year	3 Years	5 Years	10 Years
$26	$80	$141	$318

Primary Investment Policies

Primary Risks

The Fund is designed for investors with a low tolerance for risk; however, the Fund’s performance could be hurt by:

• Manager risk , which is the chance that poor security selection will cause the Fund to underperform relevant benchmarks or other funds with a similar investment objective.

Annual Total Returns

Annual Total Returns—Investor Shares ¹

1 The year-to-date return as of the most recent calendar quarter, which ended on September 30, 2009, was 0.39%.

Average Annual Total Returns for Periods Ended December 31, 2008


	1 Year	5 Years	10 Years
Vanguard Federal Money Market Fund	2.53%	3.28%	3.42%
Comparative Benchmarks
Citigroup 3-Month U.S. Treasury Bill Index
(reflects no deduction for fees or expenses)	1.80%	3.10%	3.30%
U.S. Government Money Market Funds Average	1.71	2.68	2.85

Investment Advisor

The Vanguard Group, Inc.

Portfolio Manager

John C. Lanius, Portfolio Manager of Vanguard. He has managed the Fund since 2007.

Tax Information

Financial Intermediary Compensation

The Fund and its investment advisor do not pay financial intermediaries for sales of Fund shares or related services.

Vanguard Admiral Treasury Money Market Fund

Investment Objective

The Fund seeks to provide current income while maintaining liquidity and a stable share price of $1.

Fees and Expenses

The following tables describe the fees and expenses you may pay if you buy and hold shares of the Fund.


Shareholder Fees
(Fees paid directly from your investment)
Sales Charge (Load) Imposed on Purchases	None
Purchase Fee	None
Sales Charge (Load) Imposed on Reinvested Dividends	None
Redemption Fee	None


Annual Fund Operating Expenses
(Expenses that you pay each year as a percentage of the value of your investment)
Management Expenses	0.09%
12b-1 Distribution Fee	None
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.12% ¹

Example


1 Year	3 Years	5 Years	10 Years
$12	$39	$68	$154

Primary Investment Policies

Primary Risks

The Fund is designed for investors with a low tolerance for risk; however, the Fund’s performance could be hurt by:

• Manager risk , which is the chance that poor security selection will cause the Fund to underperform relevant benchmarks or other funds with a similar investment objective.

Annual Total Returns

The following bar chart and table are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns compare with those of comparative benchmarks . The last line item in the table is derived from data provided by Lipper Inc. Keep in mind that the Fund’s past performance does not indicate how the Fund will perform in the future. Updated performance information is available on our website at www.vanguard.com or by calling Vanguard toll-free at 800-662-7447 .

Annual Total Returns—Investor Shares ¹

1 The year-to-date return as of the most recent calendar quarter, which ended on September 30, 2009, was 0.24%.

Average Annual Total Returns for Periods Ended December 31, 2008


	1 Year	5 Years	10 Years
Vanguard Admiral Treasury Money Market Fund	2.10%	3.13%	3.31%
Comparative Benchmarks
iMoneyNet Money Fund Report’s Average 100% Treasury Fund	1.13%	2.39%	2.67%
U.S. Treasury Money Market Funds Average	1.11	2.44	2.66

Investment Advisor

The Vanguard Group, Inc.

Portfolio Manager

David R. Glocke, Principal of Vanguard. He has managed the Fund since 1997.

Tax Information

Financial Intermediary Compensation

The Fund and its investment advisor do not pay financial intermediaries for sales of Fund shares or related services.

More on the Funds

This prospectus offers the Funds’ Investor Shares and is intended for participants in employer-sponsored retirement or savings plans. Another version—for investors who would like to open a personal investment account—can be obtained by calling Vanguard at 800-662-7447.

Plain Talk About Costs of Investing

Costs are an important consideration in choosing a mutual fund. That’s because

you, as a shareholder, pay the costs of operating a fund, plus any transaction

costs incurred when the fund buys or sells securities. These costs can erode a

substantial portion of the gross income or the capital appreciation a fund

achieves. Even seemingly small differences in expenses can, over time, have a

dramatic effect on a fund’s performance.

Market Exposure

invests more than 25% of its assets in money market instruments issued by financial services companies.

Plain Talk About Money Market Instruments

The term “money market instruments” refers to a variety of short-term, liquid

investments, usually with maturities of 397 days or less. Some common types

are Treasury bills and notes , which are securities issued by the U.S. government;

commercial paper , which are promissory notes issued by large companies or

financial firms; banker’s acceptances , which are credit instruments guaranteed by

banks; and negotiable certificates of deposit , which are issued by banks in large

denominations. Money market securities can pay fixed, variable, or floating rates

of interest.

Security Selection

Each Fund is subject to manager risk, which is the chance that poor security selection will cause the Fund to underperform relevant benchmarks or other funds with a similar investment objective.

The Funds are generally managed without regard to tax ramifications.

Plain Talk About Credit Quality

A money market instrument’s credit-quality rating is an assessment of the

issuer’s ability to pay interest and, ultimately, to repay the principal. The lower the

rating by one of the independent bond-rating agencies (for example, Moody’s or

Standard & Poor’s), the greater the chance—in the rating agency’s opinion—that

the issuer will default, or fail to meet its payment obligations. Direct U.S. Treasury

obligations, along with other securities backed by the “full faith and credit” of the

U.S. government, carry the highest credit ratings. All things being equal, money

market instruments with greater credit risk offer higher yields.

The Prime Money Market Fund invests in commercial paper, U.S. Treasury and agency securities, certificates of deposit, banker’s acceptances, and other money market securities. Commercial paper must be rated at least Prime-1 by Moody’s Investors Service, Inc. or A-1 by Standard & Poor’s. Securities that are unrated must be issued by a company with a debt rating of A3 or better by Moody’s or A– or better by Standard & Poor’s. The Prime Money Market Fund also invests in short-term corporate, state, and municipal obligations rated A3 or better by Moody’s or A– or better by Standard & Poor’s, as well as in securities that are considered suitable for the Federal Money Market Fund as described in this prospectus .

The Admiral Treasury Money Market Fund invests solely in securities whose interest and principal payments are backed by the full faith and credit of the U.S. government. At least 80% of the Fund ’s assets will always be invested in U.S. Treasury securities. The remainder of the Fund ’s assets may include securities issued by U.S. governmental agencies such as the GNMA, the Small Business Administration, and the Federal Financing Bank.