Santa Clara, CA and St. Louis, USA - January 21, 1998. Affymetrix, Inc. (NASDAQ: AFFX) and bioMérieux Vitek, Inc., announced today that bioMérieux has exercised its option to expand the 1996 bacteriology collaboration agreement between the companies to include the development of clinical diagnostic tests using Affymetrix GeneChip(R) probe arrays. These new products will be used to detect sequence variations in the HIV genome. This agreement also includes the development of new diagnostic genotyping tests to detect microbial contamination of food and cosmetic products.

Under the terms of the expanded non-exclusive agreement, bioMérieux will apply Affymetrix GeneChip technology towards the development of HIV genotyping and microbial contamination tests that will run on an instrumention platform being developed by bioMérieux. In addition, in order to accelerate bioMérieux’s commercialization of these assays, Affymetrix will collaborate with bioMérieux on the development of GeneChip probe arrays that will be read on Affymetrix’ GeneChip platform. In return, Affymetrix will receive upfront and milestone payments for both the HIV and microbial contamination detection assays. Once the assays are developed, Affymetrix will manufacture DNA probe arrays for bioMérieux and receive royalties on commercial sales of the products by bioMérieux. bioMérieux is responsible for all costs associated with developing the instrumention for these assays as well as the costs associated with the regulatory approval of all products it develops in collaboration with Affymetrix.

"We are pleased to strengthen our collaboration with bioMérieux, a leading company in infectious disease and industrial testing," said Stephen P.A. Fodor, Ph.D., President and Chief Executive Officer of Affymetrix. "bioMérieux’s commitment to developing these new applications of our technology should provide new products to increase the safety of food and cosmetic products."

"This agreement emphasizes bioMérieux’s commitment to remain a world leader in the fields of infectious diseases and food and cosmetic testing for microbial contamination," said Philippe Archinard, Corporate Executive Vice President of bioMérieux. "Expanded access to additional GeneChip-based assays and to Affymetrix’ existing instrumentation platform will enable bioMérieux to accelerate the development of a comprehensive set of diagnostic tools that will dramatically improve timeliness, effectiveness, accuracy and overall benefit-to- cost ratio to treat infectious diseases and to guarantee the safety of industrial products."

Affymetrix has developed and intends to establish its GeneChip system as the platform of choice for acquiring, analyzing and managing complex genetic information in order to improve the diagnosis, monitoring and treatment of disease. The Company's GeneChip system consists of disposable DNA probe arrays containing gene sequences on a chip, reagents for use with the probe arrays, a scanner and other instruments to process the probe arrays and software to analyze and manage genetic information.

bioMérieux Vitek, Inc., is part of the French bioMérieux Group, a major player in the fields of infectious disease diagnostics and industrial microbiological controls. With FRF 3 billion in annual sales in 1997 and 75% of the total in international business, the bioMérieux Group ranks among the world’s top biological diagnostics companies.
All statements in this press release that are not historical are forward-looking statements. 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, uncertainties relating to technological approaches, product development, manufacturing, and market acceptance, 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. These and other risk factors are discussed in Affymetrix' Registration Statement on Form S-3 filed with the Securities and Exchange Commission ("SEC") on October 17, 1997, and in periodic reports filed with the SEC, including the Company’s annual report on Form 10-K for the year ended December 31, 1996 and quarterly report on Form 10-Q for the quarter ended September 30, 1997. 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. Affymetrix, GeneChip and the Affymetrix logo are registered trademarks used by Affymetrix.