ARJ Arch Chemicals

The Arch Chemicals, Inc. Board of Directors on April 28, 2011 declared a quarterly dividend of 20-cents on each share of Arch Chemicals (NYSE:ARJ) common stock. The dividend is payable on June 15, 2011 to shareholders of record at the close of business on May 15, 2011.

Headquartered in Norwalk, Connecticut (USA), Arch Chemicals, Inc. is a global Biocides company with annual sales of over $1 billion. Arch and its subsidiaries provide innovative, chemistry-based and related solutions to destroy or to selectively inhibit the growth of harmful microorganisms. The Company is concentrated in the areas of water treatment, personal care, health and hygiene, industrial preservation and protection, and wood treatment. Arch Chemicals operates in two segments:  Biocides Products and Performance Products. Together with its subsidiaries, Arch has approximately 3,000 employees and manufacturing and customer-support facilities in North and South America, Europe, Asia, Australia and Africa.

CONTACT: Investor contact:
         Mark E. Faford
         (203) 229-3820
         mefaford@archchemicals.com
         
         Press contact:
         Dale N. Walter
         (203) 229-3033
         dnwalter@archchemicals.com