On June 19, 2012, Affymetrix, Inc. ("Affymetrix") entered into an underwriting agreement (the "Underwriting Agreement") with Citigroup Global Markets Inc. and Morgan Stanley & Co. LLC as representatives of the several underwriters named in the agreement to sell $105,000,000 aggregate principal amount of 4.00% Convertible Senior Notes due 2019 (the "Notes"). The Notes are expected to be issued and sold in a public offering pursuant to the Company's effective shelf registration statement on Form S-3 (File No. 333-181781) filed with the Securities and Exchange Commission (the "SEC") and the prospectus included therein, as supplemented by the preliminary prospectus supplement dated June 18, 2012, a free writing prospectus dated June 19, 2012 and the final prospectus supplement dated June 19, 2012. Affymetrix has granted the underwriters an option to purchase up to $10.0 million aggregate principal amount of additional Notes on the same terms and conditions, solely to cover over-allotments, if any.

Affymetrix expects the net proceeds from the offering of the Notes to be approximately $100.3 million (assuming no exercise of the underwriters' over-allotment option), after deducting underwriting discounts and estimated offering expenses. 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.

The above description of the Underwriting Agreement is qualified in its entirety by reference to the Underwriting Agreement, which is filed as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference.

(d) Exhibits.

Exhibit
No.                                       Description

99.1         Underwriting Agreement dated June 19, 2012, by and among Affymetrix,
             Inc. and Citigroup Global Markets Inc. and Morgan Stanley & Co. LLC,
             as representatives of the several underwriters named therein.