Sigma-Aldrich Opens European Headquarters in St. Gallen, Switzerland

ST. LOUIS, April 4, 2011 - Sigma-Aldrich Corporation (Nasdaq: SIAL) opened its European Regional
Headquarters today in St. Gallen, Switzerland. The new Einstein Facility
located in the heart of St. Gallen will be home to approximately 50
employees.

(Logo: photos.prnewswire.com/prnh/20050215/CGSIGMAALLOGO )

Establishing a European Regional Headquarters represents a critical
operational milestone for the Company - bringing its European management
together in one location to more effectively serve customers and to
accelerate the growth of Sigma-Aldrich outside the U.S. More than sixty
percent of Sigma-Aldrich's global sales come from non-U.S. entities and that
percentage continues to grow.

"Having our management team together at one site will enable stronger
leadership and direction for major supply chain and sales functions, which
will result in more efficient management processes and faster decision
making," said Michael Harris, Vice President, Managing Director EMEA. "This
energy will help accelerate the future growth of the Company."

Sigma-Aldrich has been operating in the canton of St. Gallen since 1989.
"We have always had a good relationship with the authorities of the Canton,"
said Harris. "When it came time to pick a location for our headquarters, we
quickly determined that St. Gallen was the clear best choice. The city is
only 30 minutes from our Buchs manufacturing facility, proximate to the
Zurich international airport and is well known for its business-friendly
environment."

About Sigma-Aldrich: Sigma-Aldrich is a leading Life Science and High
Technology company committed to Enabling Science to Improve the Quality of
Life. Its chemical and biochemical 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. The Company has customers
in life science companies, university and government institutions, hospitals,
and in industry. More than one million scientists and technologists use its
products. Sigma-Aldrich operates in 40 countries and has 7,900 employees
providing excellent service worldwide. For more information about
Sigma-Aldrich, please visit its award-winning website at
www.sigma-aldrich.com.

Sigma-Aldrich is a trademark of Sigma-Aldrich Biotechnology L.P. and
Sigma-Aldrich Co.

Kirk Richter, +1-314-286-8004, kirk.richter at sial.com, or Media Inquiries, Melissa Jacobs, +1-314-236-8720, melissa.jacobs at sial.com, both of Sigma-Aldrich