Charles River Laboratories International (CRL) 10-Q 2006 Q3 Quarterly report

Exhibit 32.1

CERTIFICATION 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 on Form 10-Q for the period ended September 30, 2006 of Charles River Laboratories International, Inc. (the “Company”) as filed with the Securities and Exchange Commission on the date hereof (the “Report”), the undersigned, James C. Foster, the Chairman, Chief Executive Officer and President, and Thomas F. Ackerman, Corporate Executive Vice President and Chief Financial Officer, each hereby certifies, to the best of his knowledge and pursuant to 18 U.S.C. Section 1350, that:

(1)the Report fully complies with the requirements of Section 13(a) or 15(d) 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.

Dated:	November 9, 2006	/s/ JAMES C. FOSTER
		James C. Foster
		Chairman, Chief Executive Officer & President
		Charles River Laboratories International, Inc.
Dated:	November 9, 2006	/s/ THOMAS F. ACKERMAN
		Thomas F. Ackerman
		Corporate Executive Vice President & Chief Financial Officer
		Charles River Laboratories International, Inc.