EXHIBIT 32.2

                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 annual report on Form 10-K for the period ending
December 27, 2003 of Charles River Laboratories International, Inc. (the
"Company") as filed with the Securities and Exchange Commission on the date
hereof (the "Report"), the undersigned, Chief Financial Officer of the Company,
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.


                             /s/ Thomas F. Ackerman
                             -------------------------------------------------
                             Thomas F. Ackerman
                             Senior Vice President and Chief Financial Officer
Dated: March 8, 2004         Charles River Laboratories International, Inc.