ASGN (ASGN) 10-Q 2005 Q2 Quarterly report

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 June 30, 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:	August 9, 2005	By:	/s/ Peter Dameris
			Peter Dameris
			Chief Executive Officer and President
Date:	August 9, 2005	By:	/s/ Michael J. Holtzman
			Michael J. Holtzman
			Senior Vice President, Finance
			and Chief Financial Officer

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