SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549

                                  -------------

                                  SCHEDULE 13D*
                                 (Rule 13d-101)

             INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
            TO RULE 13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO
                                  RULE 13d-2(a)

                    Under the Securities Exchange Act of 1934
                               (Amendment No. )(1)

                 Charles River Laboratories International, Inc.
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                                (Name of Issuer)

                     Common Stock, $0.01 par value per share
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                         (Title of Class of Securities)

                                    159864107
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                                 (CUSIP Number)

                              Marc Weingarten, Esq.
                            Schulte Roth & Zabel LLP
                                919 Third Avenue
                            New York, New York 10022
                                 (212) 756-2000
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                  (Name, Address and Telephone Number of Person
                Authorized to Receive Notices and Communications)

                                  May 26, 2010
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                          (Date of Event which Requires
                            Filing of This Statement)



         If the filing person has previously filed a statement on Schedule 13G
to report the acquisition that is the subject of this Schedule 13D, and is
filing this schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the
following box. [ ]

         NOTE: Schedules filed in paper format shall include a signed original
and five copies of the schedule, including all exhibits. See Rule 13d-7 for
other parties to whom copies are to be sent.

                         (Continued on following pages)

                               (Page 1 of 6 Pages)

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(1) The remainder of this cover page shall be filled out for a reporting
person's initial filing on this form with respect to the subject class of
securities, and for any subsequent amendment containing information which would
alter disclosures provided in a prior cover page.




   The information required on the remainder of this cover page shall not be
deemed to be "filed" for the purpose of Section 18 of the Securities Exchange
Act of 1934 ("Act") or otherwise subject to the liabilities of that section of
the Act but shall be subject to all other provisions of the Act (however, see
the Notes)





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CUSIP NO.      159864107           SCHEDULE 13D           PAGE 2 OF 6 PAGES
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    1       NAME OF REPORTING PERSON
            I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

            JANA PARTNERS LLC
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    2       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*       (a) [ ]
                                                                    (b) [ ]

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    3       SEC USE ONLY

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    4       SOURCE OF FUNDS*

            AF
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    5       CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDING IS REQUIRED PURSUANT
            TO ITEM 2(d) or 2(e)                                         [ ]

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    6       CITIZENSHIP OR PLACE OF ORGANIZATION

            Delaware
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                         7      SOLE VOTING POWER

                                4,657,695
                      ---------------------------------------------------------
 NUMBER OF               8      SHARED VOTING POWER
 SHARES
BENEFICIALLY                    -0-
  OWNED BY            ---------------------------------------------------------
   EACH                  9      SOLE DISPOSITIVE POWER
 REPORTING
PERSON WITH                      4,657,695
                      ---------------------------------------------------------
                         10     SHARED DISPOSITIVE POWER

                                -0-
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    11      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH PERSON

                                4,657,695
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    12      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
            CERTAIN SHARES*
                                                                        [ ]
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    13      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

            7.0%
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    14      TYPE OF REPORTING PERSON*

            IA
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                     * SEE INSTRUCTIONS BEFORE FILLING OUT!





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CUSIP NO.      159864107           SCHEDULE 13D           PAGE 3 OF 6 PAGES
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Item 1.       Security and Issuer.

       This statement on Schedule 13D relates to the shares ("Shares") of common
stock, $0.01 par value per share, of Charles River Laboratories International,
Inc., a Delaware corporation (the "Issuer"). The principal executive office of
the Issuer is located at 251 Ballardvale Street, Wilmington, Massachusetts
01887.

Item 2.       Identity and Background.

        (a) This statement is filed by JANA Partners LLC, a Delaware limited
liability company (the "Reporting Person"). The Reporting Person is a private
money management firm which holds the Shares of the Issuer in various accounts
under its management and control, including but not limited to, 270,182 Shares
(the "SP13 Shares") held in Segregated Portfolio 13 ("SP13"), a managed account
for which the Reporting Person serves as investment manager. The principals of
the Reporting Person are Barry Rosenstein and Gary Claar (the "Principals").

        (b) The principal business address of the Reporting Person and the
Principals is 767 Fifth Avenue, 8th Floor, New York, New York 10153.

        (c) The principal business of the Reporting Person and the Principals is
investing for accounts under their management.

        (d) Neither the Reporting Person nor the Principals has, during the last
five years, been convicted in a criminal proceeding (excluding traffic
violations or similar misdemeanors).

        (e) Neither the Reporting Person nor the Principals has, during the last
five years, been a party to a civil proceeding of a judicial or administrative
body of competent jurisdiction and as a result of such proceeding was or is
subject to a judgment, decree or final order enjoining future violations of, or
prohibiting or mandating activities subject to, federal or state securities laws
or finding any violation with respect to such laws.

        (f) The Reporting Person is a limited liability company organized in
Delaware. The Principals are citizens of the United States of America.

Item 3.       Source and Amount of Funds or Other Consideration.

       The 4,657,695 Shares reported herein by the Reporting Person, were
acquired at an aggregate purchase price of approximately
$148.7 million.  The






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CUSIP NO.      159864107           SCHEDULE 13D           PAGE 4 OF 6 PAGES
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Shares beneficially owned by the Reporting Person were acquired with investment
funds in accounts under management.

Item 4.       Purpose of Transaction.

        The Reporting  Person acquired the Shares because it believes the Shares
are undervalued and represent an attractive investment opportunity. On June 3rd,
2010,  representatives  of the Reporting Person met with  representatives of the
Issuer including the Chairman,  President & CEO of the Issuer and the Chairman &
CEO of WuXi PharmaTech  (Cayman) Inc. ("WuXi") in the Reporting Person's offices
to discuss the Issuer's proposed  acquisition of WuXi. In a letter sent today to
the Issuer and  attached as Exhibit B, the  Reporting  Person  stated its belief
that the proposed WuXi  acquisition is suboptimal for the Issuer's  shareholders
and its intention to vote against the issuance of the Issuer's  shares  required
to complete such acquisition.

        Except as set forth herein or as would occur upon  completion  of any of
the actions  discussed herein,  including in any Exhibits hereto,  the Reporting
Person has no present plan or proposal  that would relate to or result in any of
the matters set forth in  subparagraphs  (a)-(j) of Item 4 of Schedule  13D. The
Reporting  Person intends to review its investment in the Issuer on a continuing
basis and may engage in  discussions  with  management,  the board of directors,
other  shareholders  of the Issuer and other  relevant  parties  concerning  the
business, operations, management, board compensation,  strategy and future plans
of the Issuer. Depending on various factors including,  without limitation,  the
Issuer's  financial  position  and  strategic  direction,  the  outcome  of  the
discussions  and  actions  referenced  above,  actions  taken  by the  board  of
directors,  price levels of the Shares, other investment opportunities available
to the  Reporting  Person,  conditions  in the  securities  market  and  general
economic and industry  conditions,  the Reporting  Person may in the future take
such  actions  with  respect  to  its  investment  in  the  Issuer  as it  deems
appropriate  including,  without  limitation,  purchasing  additional  Shares or
selling some or all of its Shares,  engaging in short  selling of or any hedging
or similar transactions with respect to the Shares and/or otherwise changing its
intention  with  respect to any and all  matters  referred in Item 4 of Schedule
13D.

Item 5.       Interest in Securities of the Company.

        (a) The aggregate percentage of Shares reported to be beneficially owned
by the Reporting Person is based upon 66,191,029 Shares outstanding, which is
the total number of Shares outstanding as of April 15, 2010 as reported in the
Issuer's Quarterly Report on Form 10-Q filed on April 29, 2010 for the period
ended March 27, 2010.

       As of the close of business on June 4, 2010, the Reporting Person may be
deemed to beneficially own 4,657,695 Shares constituting approximately 7.0% of
the Shares outstanding.





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CUSIP NO.      159864107           SCHEDULE 13D           PAGE 5 OF 6 PAGES
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        (b) The Reporting Person has sole voting and dispositive powers over the
4,657,695 Shares, which powers are exercised by the Principals. Notwithstanding
the foregoing, pursuant to a Subadvisory Agreement with SP13, in certain
circumstances SP13 has the right to override the voting decisions made by the
Reporting Person with respect to securities held in SP13, including the SP13
Shares, and has the right to terminate its Subadvisory Agreement with the
Reporting Person.

        (c) Information concerning transaction in the Shares effected by the
Reporting Person during the past sixty days is set forth in Appendix A hereto
and is incorporated herein by reference. All of the transactions in Shares
listed hereto were effected in open market purchases on the New York Stock
Exchange through various brokerage entities.

        (d) No person (other than the Reporting Person) is known to have the
right to receive or the power to direct the receipt of dividends from, or the
proceeds from the sale of, the Shares.

        (e) Not applicable.

Item 6.       Contracts, Arrangements, Understandings or Relationships with
              Respect to Securities of the Company.

None.


Item 7.       Material to be Filed as Exhibits.

    1.   Exhibit A: Transactions In The Issuer During The Last 60 Days

    2.   Exhibit B: Letter to James C. Foster dated June 7, 2010





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CUSIP NO.      159864107          SCHEDULE 13D            PAGE 6 OF 6 PAGES
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                                   SIGNATURES

        After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.



Dated:  June 7, 2010



                                                JANA PARTNERS LLC


                                                By: /s/ Jennifer Fanjiang
                                                -------------------------
                                                Name:  Jennifer Fanjiang
                                                Title: Deputy General Counsel