AltheaDx Will Offer Affymetrix Technology as Part of a Complete Biomarker Discovery and Development Platform

SAN DIEGO, CA–Apr 15, 2008 — AltheaDx, a leading provider of contract testing services to the pharmaceutical and biotechnology industry, today announced a supply and service provider agreement with Affymetrix Inc. (NasdaqGS:AFFX – News). The agreement enables AltheaDx to offer complete biomarker discovery and development services based on the Affymetrix GeneChip® microarray platform. AltheaDx, a recent spin-out of Althea Technologies, is making the services available to customers worldwide.

AltheaDx will utilize the Affymetrix genotyping and gene expression technology to identify novel biomarkers and analyze gene pathways critical to the development and progression of cancer. The Affymetrix technology delivers a more comprehensive view of genome activity and enables researchers to better understand human diversity and the molecular basis of complex disease.

“The Affymetrix microarray platform is a great addition to AltheaDx Express Pathway biopharma partnership program, which we currently utilize for custom biomarker and companion diagnostic development for oncology therapeutics. Our Express Pathway program has produced several biopharma partnerships for development and utilization of multi-parameter genetic biomarkers in clinical trials,” said Cyrus K. Mirsaidi, Vice President Business Development, Sales and Marketing for AltheaDx.

“The Affymetrix platform enables researchers to make more informed drug-development decisions, which in turn significantly streamlines the drug-development process and, therefore, the time to market,” said Ramsey Hashem, Senior Vice President of Global Commercial Operations at Affymetrix. “AltheaDx strengthens our Authorized Service Provider Program and provides our customers with more options to better meet the evolving drug discovery market.”

About AltheaDx

AltheaDx is bringing cancer diagnostics into clinical use. The ultimate goal of AltheaDx is to win the war against cancer by reducing the time, risk, and cost of drug development and by providing comprehensive oncology testing services.

For more information about AltheaDx, visit www.altheadx.com.

About Affymetrix

Affymetrix GeneChip® 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 the agreement with AltheaDx 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 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.