Exhibit 32.1

Certifications of Chief Executive Officer and Chief Financial Officer

Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 (18 U.S.C. Section 1350)

The undersigned, the Chief Executive Officer and the Chief Financial Officer of On Assignment, Inc. (the “Company”), each hereby certifies that, to his knowledge on the date hereof:

(a)   the Quarterly Report on Form 10-Q of the Company for the period ended March 31, 2005 filed on the date hereof with the Securities and Exchange Commission (the “Report”) fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

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

Date:		May 10, 2005		By:	/s/ Peter Dameris
					Peter Dameris
					Chief Executive Officer and President
Date:		May 10, 2005		By:	/s/ Michael J. Holtzman
					Michael J. Holtzman
					Senior Vice President, Finance and
					Chief Financial Officer

A signed original of this written statement required by Section 906, or other document authenticating, acknowledging, or otherwise adopting the signature that appears in typed form within the electronic version of this written statement required by Section 906, has been provided to the Company and will be retained by the Company and furnished to the Securities and Exchange Commission or its staff upon request.

The foregoing certification is being furnished to the Securities and Exchange Commission as our exhibit to the Form 10-Q and shall not be deemed to be considered filed as part of the Form 10-Q.