Exhibit 32.2

Certification of Chief Financial Officer Pursuant to

18 U.S.C. Section 1350,

As Adopted Pursuant to

Section 906 of the Sarbanes-Oxley Act of 2002

In connection with the Quarterly Report of Cepheid (the Company) on Form 10-Q for the quarter ended June 30, 2006, as filed with the Securities and Exchange Commission on August 8, 2006, and the Report of the Company on Form 10-Q/A filed with the Securities and Exchange Commission on the date hereof (the Report), I, John R. Sluis, as Vice President of Finance and Chief Financial Officer of the Company, hereby certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

(1) The Report fully complies with the requirements of Section 13(a) of the Securities Exchange Act of 1934; and

(2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Date: September 11, 2006

/s/ John R. Sluis  

John R. Sluis 

Senior Vice President, Finance and
Chief Financial Officer 

This certification accompanies this report pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, is not deemed filed with the Securities and Exchange Commission and is not to be incorporated by reference into any filing of the Company under the Securities Act of 1933 or the Securities Exchange Act of 1934 (whether made before or after the date of the Report), irrespective of any general incorporation language contained in such filing.