Santa Clara, California and Rockville, Maryland
April 15, 2002

Affymetrix, Inc. (Nasdaq: AFFX) and The Institute for Genomic Research (TIGR) today announced the completion of a joint GeneChip(R) Arabidopsis thaliana array design representing approximately 24,000 genes on a single microarray.

The new GeneChip Arabidopsis array is based on information from the international Arabidopsis sequencing project. Under a cooperative agreement with the National Science Foundation, TIGR led the effort to re-annotate the Arabidopsis genome, which resulted in the collaboration with Affymetrix on the new array design. The new array takes advantage of Affymetrix' advanced design methods to allow representation of approximately three times more information on a single array than Affymetrix' previous Arabidopsis product, introduced in 2000.

"TIGR's extensive work with the Arabidopsis genome made them an excellent collaborator in the design of this new array," said Alan Dance, Sr. Vice President, Corporate Marketing, at Affymetrix. "The substantial improvements TIGR made over the past year in Arabidopsis genome annotation are incorporated into this new array and will give scientists a powerful tool for a wide variety of plant studies."

"Our collaboration with Affymetrix has been very successful and this new microarray will help scientists get the robust and reproducible Arabidopsis genome data they need," said Chris Town, Ph.D., a lead scientist in TIGR's Arabidopsis project.

Arabidopsis annotation data from the TIGR database will be hosted on the NetAffx(TM) Analysis Center at www.affymetrix.com and the TIGR website at www.tigr.org. The GeneChip Arabidopsis array is now available to Affymetrix customers as a Made-to-Order product. Made-to-Order arrays are shipped approximately four weeks from the order date.

TIGR is a not-for-profit research institute, based in Rockville, Maryland, that conducts research involving the structural, functional, and comparative analysis of genomes and gene products in bacteria, archaea, and eukaryotes, both plant and animal.

Affymetrix is a market leader in creating breakthrough tools that are driving the genomic revolution. By applying the principles of semiconductor technology to the life sciences, Affymetrix develops and commercializes systems that help scientists alleviate human suffering and improve the quality of life. The Company's customers include pharmaceutical, biotechnology, agrochemical, diagnostics and consumer products companies as well as academic, government and other non-profit research
institutes. Affymetrix offers an expanding portfolio of integrated products and services, including its integrated GeneChip platform, to address growing markets focused on understanding the relationship between genes and human health.

Affymetrix, GeneChip and the Affymetrix logo are registered trademarks used by Affymetrix Inc.