ST. LOUIS, Sigma-Aldrich® (NASDAQ: SIAL) — At the Board of Directors meeting held today, the Directors declared a quarterly cash dividend of $.18 per share. The dividend is payable on December 15, 2011 to shareholders of record on December 1, 2011.

The Board of Directors also approved a ten million share increase in the Company’s repurchase authorization. This action brings the total authorization to 110 million shares of which 97.625 million shares have been acquired. Shares repurchased are held as treasury shares. The Company expects to offset the dilutive impact of issuing share based compensation with future repurchases. The Company expects to repurchase the 12.375 million remaining authorized shares, but the timing and number of shares purchased, if any, depends upon market conditions and other factors.

About Sigma-Aldrich: Sigma-Aldrich is a leading Life Science and High Technology company. Our biochemical and organic chemical products and kits are used in scientific research, including genomic and proteomic research, biotechnology, pharmaceutical development, and as key components in pharmaceutical, diagnostic and other high technology manufacturing. We have customers in life science companies, university and government institutions, hospitals and in industry. Over one million scientists and technologists use our products. Sigma-Aldrich operates in 40 countries and has over 8,300 employees providing excellent service worldwide. We are committed to accelerating our Customers’ success through leadership in Life Science, High Technology and Service. For more information about Sigma-Aldrich, please visit our award winning web site at www.sigma-aldrich.com.