June 30, 2008

Affymetrix Technology Used to Discover Molecular Mechanisms of Liver Disease

Affymetrix Inc. (Nasdaq:AFFX) today announced that a team of researchers at the Fraunhofer Institute in Germany is using Affymetrix' Whole Transcript (WT) gene expression technology to better understand the molecular basis of drug-induced liver injury (DILI). The ultimate goal of the project is to develop a diagnostic array that can detect signals of liver toxicity earlier and more accurately than traditional techniques.

DILI is one of the most common side effects of pharmacotherapy and the most frequent reason why registered drugs are withdrawn from the market.(1) Currently, there is no reliable method to forecast the progression of various types of DILI. A diagnostic tool that can effectively predict liver disease could save drug companies around $2 billion annually in development expenses in the United States alone.(2)

Professor Juergen Borlak, director, Fraunhofer Institute of Toxicology and Experimental Medicine (ITEM) and head of the Institute of Pharmaco- and Toxicogenomics at the Hannover Medical School (MHH), is leading the study. The MHH is Europe's largest liver transplant center.

Professor Borlak's team is using the Affymetrix Exon and Gene Arrays to analyze the molecular mechanisms involved in the development of DILI. The Affymetrix WT technology enables researchers to survey both gene- and exon-level expression, as well as alternative splicing patterns on the whole-genome scale. Any one of these transcripts can be used to develop a new treatment or diagnostic.

"Applying genomic sciences to toxicology can dramatically improve drug safety," said Dr. Borlak. "The Affymetrix WT technology enables us to see the real biology to better identify susceptible genes and potential gene targets for novel pharmacotherapeutic treatments."

"Professor Borlak is recognized around the world for his efforts toward finding new technologies to safeguard drug candidates," said Kevin King, president of Affymetrix. "We are eager to see the Fraunhofer Institute's results and look forward to the commercialization of a more effective diagnostic tool for drug-induced liver injury."

Initial data from the study cohort is expected to be published by the fall of 2008. After clinical evaluation, the Fraunhofer Institute hopes to launch its diagnostic tool in the spring of 2009.

About Affymetrix

Affymetrix GeneChip(R) microarray technology is the industry-standard tool for analyzing complex genetic information. After inventing microarray technology in the late 1980s, Affymetrix scientists have been dedicated to developing innovative products that provide researchers with a more complete view of the genome. These products continue to accelerate genetic research and enable scientists to develop diagnostics and tailor treatments for individual patients by identifying and measuring the genetic information associated with complex diseases.

Today, Affymetrix technology is used by the world's top pharmaceutical, diagnostic and biotechnology companies, as well as leading academic, government and not-for-profit research institutes. More than 1,700 systems have been shipped around the world and more than 12,000 peer-reviewed papers have been published using the technology.

Affymetrix is headquartered in Santa Clara, Calif., and has manufacturing facilities in Sacramento, Calif., Cleveland, Ohio, and Singapore. The company has about 1,100 employees worldwide and maintains sales and distribution operations across Europe and Asia. For more information about Affymetrix, please visit the company's website at www.affymetrix.com.

Forward-looking Statements

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 and uncertainties relating to commercial success of the agreement with the Fraunhofer Institute of Toxicology and Experimental Medicine discussed in this press release; risks of the company's ability to achieve and sustain higher levels of revenue, higher gross margins and reduced operating expenses; uncertainties related to technological approaches, manufacturing and product development; personnel retention; uncertainties related to cost and pricing of Affymetrix products; dependence on collaborative partners; uncertainties related to sole-source suppliers; risks associated with past and future acquisitions; 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, 2007, 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(R) are registered trademarks owned or used by Affymetrix Inc.

(1) From Fraunhofer Annual Report 2007: http://www.item.fraunhofer.de/english/media/index.html

(2) Based on the calculation that 19 drugs were withdrawn from the U.S. market in the last decade and each one cost around $1billion a year, contained in: Giacomini KM, et al. When good drugs go bad, Nature 446(7139): 977 (2007)