St. Louis, MO: 26th August 2005 - SAFC, a leading custom chemical manufacturer and a division of Sigma-Aldrich Corporation (NASDAQ: SIAL), announced today that its Madison, WI API manufacturing facility has completed an assessment and been granted SafeBridge certification for its pilot plant.

The assessment was completed over two days in July and involved an analysis of all systems related to potent compound handling in the facility. In addition, SafeBridge also granted recertification of Madison's kilo lab manufacturing areas. The original kilo lab assessment was completed in 2003, but the overall SafeBridge program requires a biennial recertification process to validate that systems are continuously being maintained and improved.

Commenting on the successful completion of this process, Dave Bormett, SAFC's Director of Regulatory Affairs said: "The successful completion of the pilot facility assessment fulfills our commitment to customers and employees of implementing systems across the entire Madison facility that benchmark us as an industry leader in potent compound handling. "I am pleased that our assessment scores went up across the board highlighting our focus on process improvements as we gain additional expertise in this area. We set facility-wide SafeBridge certification as a goal over three years ago and our employees have worked hard toward today's achievement."

About SAFC:

SAFC is the custom manufacturing group within Sigma-Aldrich that focuses on both biochemical production and the manufacturing of complex, multi-step organic synthesis of APIs and key intermediates. SAFC has manufacturing facilities around the world dedicated to providing manufacturing services for companies requiring a reliable partner to produce their custom manufactured materials.

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 and genomic research, biotechnology, pharmaceutical development, the diagnosis of disease and as key components in pharmaceutical 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 34 countries and has over 6,000 employees providing excellent service worldwide. We are committed to the success of our Customers, Employees and Shareholders through leadership in Life Science, High Technology and Service.

Cautionary Statement:

This release contains forward-looking statements relating to future performance, goals, strategic actions and initiatives and similar intentions and beliefs and other statements regarding Sigma-Aldrich's expectations, goals, beliefs, intentions and the like regarding future sales, earnings and other matters. These statements involve assumptions regarding Company operations, investments and conditions in the markets the Company serves. Although the Company believes its expectations are based on reasonable assumptions, such statements are subject to risks and uncertainties, including, among others, certain economic, political and technological factors. Actual results could differ materially from those stated or implied in this news release, due to, but not limited to, such factors as (1) changes in pricing and the competitive environment, (2) other changes in the business environment in which the Company operates, (3) uncertainties surrounding government healthcare reform, (4) government regulations applicable to the business, (5) the impact of fluctuations in foreign currency exchange rates, and (6) the ability to retain customers, suppliers and employees. (7) the success of research and development activities and (8) the impact of acquisitions and success in integrating and obtaining projected results from the acquisitions. The Company does not undertake any obligation to update these forward-looking statements.