<PAGE>


                                                                     Exhibit 5.1

                                  July 12, 2002

Waters Corporation
34 Maple Street
Milford, Massachusetts 01757

Dear Sir or Madam:

     We have acted as counsel for Waters Corporation, a Delaware corporation
(the "Company"), in connection with the Company's Registration Statement on Form
S-8 to be filed with the Securities and Exchange Commission on July 12, 2002
(the "Registration Statement").

     The Registration Statement covers the registration of 5,750,000 shares of
the common stock, $0.01 par value per share, of the Company (the "Shares"),
which are to be issued by the Company upon exercise of employee stock options to
be issued pursuant to the Waters Corporation Second Amended and Restated 1996
Long-Term Performance Incentive Plan (the "Plan").

     We have reviewed the corporate proceedings of the Company with respect to
the authorization of the Plan and the issuance of the Shares thereunder. We have
also examined and relied upon originals or copies, certified or otherwise
identified or authenticated to our satisfaction, of such agreements,
instruments, corporate records, certificates, and other documents as we have
deemed necessary or appropriate as a basis for the opinions hereinafter
expressed. In our examination, we have assumed the genuineness of all
signatures, the conformity to the originals of all documents reviewed by us as
copies, the authenticity and completeness of all original documents reviewed by
us in original or copy form, and the legal competence of each individual
executing any document.

     We further assume that all Shares issued upon exercise of options to be
purchased pursuant to the Plan will be issued in accordance with the terms of
such Plan.

     Subject to the limitations set forth below, we have made such examination
of law as we have deemed necessary for the purposes of this opinion. This
opinion is limited solely to the Delaware General Corporation Law, as applied by
courts located in Delaware, the applicable provisions of the Delaware
Constitution and the reported judicial decisions interpreting those laws.

     Based upon and subject to the foregoing, we are of the opinion that the
Shares, when issued and delivered as upon the exercise of options duly purchased
pursuant to the Plan and against the payment of the purchase price therefor as
provided in Plan, will be validly issued, fully paid, and non-assessable.

     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement.

                                            Very truly yours,


                                            /s/  BINGHAM MCCUTCHEN LLP

                                            BINGHAM MCCUTCHEN LLP





