SANTA CLARA, Calif.– Affymetrix Inc., (NASDAQ:AFFX) today announced that it intends to offer, subject to market and other considerations, $105 million aggregate principal amount of unsecured Convertible Senior Notes due 2019. The offering is being made pursuant to an effective shelf registration statement on Form S-3 previously filed with the Securities and Exchange Commission (the “SEC”) and a prospectus supplement filed with the SEC today. Affymetrix also expects to grant the underwriters an option to purchase up to $10 million aggregate principal amount of additional notes on the same terms and conditions, solely to cover over-allotments, if any.

Affymetrix intends to use the net proceeds from the offering to fund a portion of the purchase price for its pending acquisition of eBioscience Holding Company, Inc. In the event that the acquisition of eBioscience is not consummated and Affymetrix does not elect to redeem the notes, Affymetrix management will retain broad discretion over use of the net proceeds.

Citigroup and Morgan Stanley are acting as joint book-running managers of the offering.

This press release shall not constitute an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of these securities in any state in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state. The offering of securities may be made only by means of a base prospectus and the related prospectus supplement. Copies of these offering documents can be obtained by contacting Citigroup, Attention: Prospectus Department, Brooklyn Army Terminal, 140 58th Street, 8th Floor, Brooklyn, NY 11220, telephone: 1-877-858-5407 or Morgan Stanley, 180 Varick Street (second floor), New York, NY 10014, telephone: 1-866-718-1649 or by emailing prospectus@morganstanley.com.