Affymetrix Launches Single Array for Mouse Genome Expression Analysis
-- Over 1 million probes analyze expression levels of nearly 39,000 RNA transcripts and variants on a single array --

Santa Clara, Calif., Dec. 3, 2003 – Affymetrix, Inc., (NASDAQ: AFFX) today announced that it will start taking orders for its new GeneChip^® Mouse Genome 430 2.0 Array on Monday, December 8^th, offering researchers the entire transcribed mouse genome on a single microarray, cutting the time, labor and resources needed for any given experiment in half.

“The introduction of the Mouse 430 2.0 marks a new generation of Affymetrix tools that offer customers more information and better performance at less cost per data point,” said Alan Dance, Sr. Vice President of the Applications Business Unit. “New instruments and arrays combined with Affymetrix’ probe set strategy utilizing multiple data points to measure the hybridization of each transcript on the array offers a level of data quality unparalleled in the industry.”

The Mouse 430 2.0 Array represents the most transcripts and variants available on a single expression array, compressing all the data from the previous two-chip Mouse 430 set on a single array, while still providing Affymetrix’ superior data quality. The Mouse 430 2.0 Array covers over 39,000 transcripts, including over 34,000 well-substantiated mouse genes. The array data was compiled from several leading public mouse genome databases, ensuring open access to the underlying sequences for scientists worldwide.

Affymetrix uses 22 independent data points to measure the hybridization of each of the 39,000 transcripts on the array, providing optimal sensitivity and specificity, and the most accurate, reproducible and statistically significant results possible. 

Affymetrix’ next generation system includes the Mouse 430 2.0 Array and the recently introduced HG-U133 Human Plus 2.0 Array and new CustomExpress Arrays. The new arrays offer two thirds more data on a single chip, putting high quality, affordable whole-genome analysis within the reach of individual researchers worldwide. The new GCS 3000 Scanner, Autoloader and the FS450 fluidics station offer researchers a robust and reliable system to process this new generation of chips.  Shipments of the Mouse 430 2.0 arrays to customers will begin later this month.

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 the 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 GeneChip Mouse Genome 430 Plus 2.0 Array), 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.

For further information, please contact:

Sue Charles, Northbank Communications, +44 (0)20 7886 8150,  s.charles@northbankcommunications.com 

At Affymetrix:
Wes Conard, Senior PR Manager, +1 408 731 5791, wes_conard@affymetrix.com