SANTA CLARA, Calif., Sep 1, 2004 /PRNewswire-FirstCall via COMTEX/ -- Affymetrix, Inc., (Nasdaq: AFFX) today announced the availability of the world's first microarray instrument system for clinical diagnostics. The GeneChip System 3000Dx (GCS 3000Dx) is CE marked (Conformite Europeene) for in-vitro diagnostic use, enabling clinical laboratories in Europe to analyze microarray diagnostics, such as the Roche AmpliChip(TM) CYP450 Test. This test, which looks for genetic variations that can affect drug efficacy and cause adverse drug reactions, is the first CE marked microarray product launched through the "Powered by Affymetrix" partnership between Roche Diagnostics and Affymetrix.

Availability of the new GCS 3000Dx system offers Roche Diagnostics and other "Powered by Affymetrix" partners an in-vitro diagnostic platform to develop innovative genotyping and gene expression array-based assays that will help improve patient care and treatment.

"Affymetrix is committed to developing tools that will improve quality of life," said Stephen P.A. Fodor, Ph.D., Chairman and CEO of Affymetrix. "With the availability of microarray-based diagnostics, the healthcare community will now have access to a scalable and affordable technology to analyze the genetics of human disease."

The GCS 3000Dx instrumentation system comprises a GCS 3000Dx Scanner with AutoloaderDx, a fluidics station FS450Dx, and GCOSDx software. This is an extension of the same platform that has been used in over 1,000 clinical research publications, but is now configured for diagnostic use in the European Union. The release of the Amplichip CYP450 Test builds on Affymetrix' recent ISO certification for its instrumentation and microarray manufacturing facilities, an achievement confirming the highest levels of quality assurance.

The Roche AmpliChip CYP450 Test will allow diagnostic laboratories to identify certain naturally occurring variations in the drug metabolism genes, CYP2D6 and CYP2C19. These variations affect the rate at which an individual metabolizes many common drugs used to treat diseases including depression, schizophrenia, bi-polar disorder, cardiovascular disease treated with beta-blockers and others. Knowledge of these variations, when considered with other contributing factors, can help a physician select the best drug and set the right dose for a patient sooner, as well as avoid drugs that may cause the patient to suffer adverse reactions.

Affymetrix is working to develop a network of partnerships with companies like Roche Diagnostics to create novel array-based diagnostics in both the clinical and non-clinical markets. With this "Powered by Affymetrix" program, Affymetrix manufactures the microarrays and instruments, while the diagnostic partner develops and commercializes the test. The resulting microarray products enable users to examine genomic sequences in more detail than ever before, providing a more efficient and complete method to diagnose a wide range of conditions and create potential solutions.

About Affymetrix:

Affymetrix is a pioneer 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 enable scientists to improve quality of life. The Company's customers include pharmaceutical, biotechnology, agrichemical, 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 brand platform, to address growing markets focused on understanding the relationship between genes and human health. Additional information on Affymetrix can be found at www.affymetrix.com.

All statements in this press release that are not historical are "forward- looking statements" within the meaning of Section 21E of the Securities Exchange Act as amended, including statements regarding Affymetrix' "expectations," "beliefs," "hopes," "intentions," "strategies" or the like. Such statements are subject to risks and uncertainties that could cause actual results to differ materially for Affymetrix from those projected, including, but not limited to risks of the Company's ability to achieve and sustain higher levels of revenue, higher gross margins, reduced operating expenses, uncertainties relating to technological approaches, manufacturing, product development, market acceptance (including uncertainties relating to the performance and market acceptance of the diagnostic products discussed in this press release), personnel retention, uncertainties related to cost and pricing of Affymetrix products, dependence on collaborative partners, uncertainties relating to sole source suppliers, uncertainties relating to FDA and other regulatory approvals, competition, risks relating to intellectual property of others and the uncertainties of patent protection and litigation. These and other risk factors are discussed in Affymetrix' Form 10-K for the year ended December 31, 2003 and other SEC reports, including its Quarterly Reports on Form 10-Q for subsequent quarterly periods. Affymetrix expressly disclaims any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements contained herein to reflect any change in Affymetrix' expectations with regard thereto or any change in events, conditions, or circumstances on which any such statements are based.

NOTE: Affymetrix, the Affymetrix logo, and GeneChip are registered trademarks owned or used by Affymetrix, Inc. AmpliChip is a trademark owned or used by Roche.

SOURCE Affymetrix, Inc.

media, Wes Conard, Assoc. Director, Public Relations, +1-408-731-5791, or +1-415-385-4455, or investors, Doug Farrell, Vice President, Investor Relations, +1-408-731-5285, both of Affymetrix, Inc.

http://www.affymetrix.com