Exhibit 5.1

Pillsbury Winthrop Shaw Pittman LLP
50 Fremont Street
San Francisco, California 94105

October 4, 2005

Genomic Health, Inc.
301 Penobscot Drive
Redwood City, California 94063

Re: Registration Statement on Form S-8

Ladies and Gentlemen:

     We are acting as counsel for Genomic Health, Inc., a Delaware corporation (the “Company”), in connection with the Registration Statement on Form S-8 (the “Registration Statement”) relating to the registration under the Securities Act of 1933 (the “Act”) of 6,316,402 shares of the Company’s Common Stock, par value $0.0001 per share (the “Shares”), issuable pursuant to the Company’s 2005 Stock Incentive Plan and 2001 Stock Incentive Plan (the “Plans”).

     We have reviewed and are familiar with such corporate proceedings and other matters as we have deemed necessary for this opinion. Based upon the foregoing, we are of the opinion that the Shares have been duly authorized and, when issued and sold in accordance with the Plans, will be validly issued, fully paid and nonassessable. This opinion is limited to matters governed by the General Corporation Law of the State of Delaware.

     We hereby consent to the filing of this opinion as Exhibit 5.1 to the Registration Statement. In giving this consent, we do not thereby admit that we are within the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Securities and Exchange Commission promulgated thereunder.

     Very truly yours,

     /s/ PILLSBURY WINTHROP SHAW PITTMAN LLP