Affymetrix Announces Completion of Smallpox Array Set Developed with CDC
- Seven-Array Set Will Enable Rapid Resequencing of the Entire Smallpox Genome -

SANTA CLARA, Calif., Feb. 19 -- Affymetrix, Inc., (Nasdaq: AFFX) today announced the completion of the GeneChip(R) brand Smallpox Resequencing Array Set, seven smallpox arrays that will enable rapid resequencing of the entire smallpox genome. These arrays, developed in collaboration with the Centers for Disease Control and Prevention (CDC), contain genomic sequence common to all strains of smallpox, as well as variant DNA from different smallpox isolates.

The Affymetrix Smallpox Resequencing Array Set will be used to identify and catalog hundreds of different smallpox strains within the World Health Organization collection maintained at the CDC and will also help researchers differentiate smallpox from other orthopox viruses like monkeypox or cowpox.

The smallpox array set can potentially be used to quickly identify a new smallpox strain as well as determine if a particular strain has been genetically engineered. The array set may also have clinical applications, such as epidemiological studies and vaccine research.

"This array set joins a growing list of pathogen arrays developed using the CustomSeq(TM) Array Program, including a SARS virus array and numerous other custom arrays," said Greg Yap, Senior Marketing Director, DNA Analysis. "Through this program, researchers can design custom arrays to completely resequence an entire viral organism, such as SARS or smallpox, or design a single array to interrogate unique sequences from multiple pathogens."

Pathogen arrays can be used to identify and catalog outbreaks, as well as to compare patient outcome among different pathogen subtypes. Such arrays allow scientists to better understand which strains are most dangerous and to discover key factors in developing therapies. In addition, epidemiologists can use the arrays to study how viruses are evolving over time, during their spread into different geographies and populations.

One CustomSeq array can sequence about 30,000 bases of unique sequence quickly and with a high degree of accuracy. Compared to capillary methods, CustomSeq arrays make sequencing faster and more effective by delivering completed sequence with minimal assembly and alignment. Understanding pathogens is one of many CustomSeq array applications. Other uses of CustomSeq arrays include SNP discovery, comparative sequencing of drug targets and investigation of candidate gene regions.

For more information about CustomSeq resequencing arrays, customers may contact their Affymetrix Sales Representative, or point their browsers to www.affymetrix.com.

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 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 product development and market acceptance of the Affymetrix Smallpox Resequencing Array Set), 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, 2002 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. 

Affymetrix UK Ltd:

Voyager, Mercury Park,
Wycombe Lane, Wooburn Green
High Wycombe
HP10 0HH
UK
t: +44 (0) 1628 552500