Exhibit 3.13

                            CERTIFICATE OF AMENDMENT
                                       OF
            SECOND AMENDED AND RESTATED CERTIFICATE OF INCORPORATION
                                       OF
                               WATERS CORPORATION

     WATERS CORPORATION, a corporation organized and existing under the laws of
the State of Delaware (the "Corporation"), does hereby certify, pursuant to
Section 242 of the General Corporation Law of the State of Delaware, that:

     FIRST:  The name of the Corporation is Waters Corporation.

     SECOND: The Certificate of Incorporation of the Corporation was originally
filed with the Secretary of State of Delaware on December 6, 1991.

     THIRD:  The Second Amended and Restated Certificate of Incorporation, as
amended, of the Corporation is further amended to effect a change in Article
FOURTH thereof, relating to the authorized capital stock of the Corporation,
accordingly the first paragraph of Article FOURTH of the Second Amended and
Restated Certificate of Incorporation shall be amended to read in its entirety
as follows:

             The total number of shares of all classes which the Corporation
             shall have the authority to issue is Four Hundred Five Million
             (405,000,000) shares, all with a par value of One Cent ($.01) per
             share, of which Five Million (5,000,000) shares shall be designated
             as Preferred Stock, and Four Hundred Million (400,000,000) shares
             shall be designated as Common Stock.

     FOURTH: This amendment of the Second Amended and Restated Certificate of
Incorporation, as amended, has been duly adopted by the vote of the Board of
Directors of the Corporation, at a duly called Regular Meeting of the Board, and
thereafter duly adopted by the vote of the Corporation's stockholders at the
Annual Meeting of Stockholders.

     FIFTH:  This amendment has been duly adopted in accordance with the
provisions of Section 242 of the General Corporation Law of the State of
Delaware.

     IN WITNESS WHEREOF, Waters Corporation has caused this certificate to be
signed by Douglas A. Berthiaume, its Chairman, President and Chief Executive
Officer, and attested by Victor J. Paci, its Secretary, as of this 25/th/ day of
May, 2001.

                                       WATERS CORPORATION

                                             /s/ Douglas A. Berthiaume

                                             Chairman, President and
                                             Chief Executive Officer

ATTEST:
By:      /s/ Victor J. Paci
         Secretary