EXMGF Gunnison Copper Corporation (QB)

Excelsior Mining Corp. (TSX VENTURE: MIN)(OTCQX: EXMGF)(PINK SHEETS: EXMGF)(FRANKFURT: 3XS) ("Excelsior") is pleased to announce that today it has filed a National Instrument (NI) 43-101 Technical Report dated August 31, 2011 on SEDAR at www.sedar.com. The Report is with respect to Excelsior's resource estimate on the North Star Deposit, announced in a July 19, 2011 press release. The Report confirms no changes in the resource estimate from the July 19th release, which stated an indicated oxide copper (Cu) resource of 3.21 billion pounds (511 million tons at 0.31% Cu) and an additional inferred resource of 0.88 billion pounds Cu (159 million tons at 0.28% Cu) for the North Star Deposit. Refer to the Report for further details on the resource estimate. The North Star Deposit is part of the Gunnison Copper Property located within the copper porphyry belt in southern Arizona.

Excelsior's exploration work on the Gunnison Property is supervised by Stephen Twyerould, Fellow of AUSIMM, President and CEO of Excelsior and a Qualified Person as defined by NI 43-101. Mr. Twyerould has reviewed and approved the technical information contained in this news release.

About Excelsior

Excelsior is an exploration and development company with a copper project located within the copper porphyry belt of Arizona. The Gunnison Copper Project is located close to the required infrastructure and with its in-situ recovery potential, is intended for near-term production. The Excelsior team consists of experienced professionals with proven track records of advancing projects towards production.

Further details about Excelsior can be found at: http://www.excelsiormining.com.

ON BEHALF OF THE EXCELSIOR BOARD

Stephen Twyerould, President & CEO

Cautionary Note Regarding Forward-Looking Information

Information set forth in this news release may involve forward-looking statements under applicable securities laws. Forward-looking statements are statements that relate to future, not past, events. In this context, forward-looking statements often address expected future business and financial performance, and often contain words such as "anticipate", "believe", "plan", "estimate", "expect", and "intend", statements that an action or event "may", "might", "could", "should", or "will" be taken or occur, or other similar expressions. All statements, other than statements of historical fact, included herein including, without limitation; statements about future exploration on and the development of the Gunnison Project are forward-looking statements. By their nature, forward-looking statements involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements, or other future events, to be materially different from any future results, performance or achievements expressed or implied by such forward-looking statements. Such factors include, among others, the following risks: the need for additional financing; operational risks associated with mineral exploration; fluctuations in commodity prices; title matters; environmental liability claims and insurance; reliance on key personnel; the potential for conflicts of interest among certain officers, directors or promoters with certain other projects; the absence of dividends; competition; dilution; the volatility of our common share price and volume and the additional risks identified the management discussion and analysis section of our interim and most recent annual financial statement or other reports and filings with the TSX Venture Exchange and applicable Canadian securities regulations. Forward-looking statements are made based on management's beliefs, estimates and opinions on the date that statements are made and the Company undertakes no obligation to update forward-looking statements if these beliefs, estimates and opinions or other circumstances should change, except as required by applicable securities laws. Investors are cautioned against attributing undue certainty to forward-looking statements.

Cautionary Note Concerning Reserve and Resource Estimates

This press release uses the terms "reserves", "resources", "proven reserves", "probable reserves", "measured resources", "indicated resources" and "inferred resources". United States investors are advised that, while such terms are recognized and required by Canadian securities laws, the United States Securities and Exchange Commission (the "SEC") does not recognize them. Under United States standards, mineralization may not be classified as a "reserve" unless the determination has been made that the mineralization could be economically and legally produced or extracted at the time the reserve determination is made. Mineral resources that are not mineral reserves do not have demonstrated economic viability. United States investors are cautioned not to assume that all or any part of measured or indicated resources will ever be converted into reserves. Inferred Resources are in addition to Measured and Indicated Resources. Further, inferred resources have a great amount of uncertainty as to their existence and as to whether they can be mined legally or economically. It cannot be assumed that all or any part of the inferred resources will ever be upgraded to a higher category. Therefore, United States investors are also cautioned not to assume that all or any part of the inferred resources exist, or that they can be mined legally or economically. Disclosure of "contained ounces" is permitted disclosure under Canadian regulations, however, the SEC normally only permits issuers to report "resources" as in place tonnage and grade without reference to unit measures. Accordingly, information concerning descriptions of mineralization and resources contained in this release may not be comparable to information made public by United States companies subject to the reporting and disclosure requirements of the SEC.

National Instrument 43-101 Standards of Disclosure for Mineral Projects ("NI 43-101") is a rule developed by the Canadian Securities Administrators, which established standards for all public disclosure an issuer makes of scientific and technical information concerning mineral projects. Unless otherwise indicated, all reserve and resource estimates referred to in this press release or released by the Company in the future have been or will be prepared in accordance with NI 43-101 and the Canadian Institute of Mining, Metallurgy and Petroleum Classification System. The requirements of NI 43-101 are not the same as those of the SEC and any reserves reported by the Company in compliance with NI 43-101 may not qualify as reserves under the SEC's standards.

Neither the TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release, and no securities regulatory authority has either approved or disapproved of the contents of this release.

Contacts: Excelsior Mining Corp. Investor Relations 604-681-8030 604-681-8039 (FAX) www.excelsiormining.com