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                                   Exhibit 5.1
                         TESTA, HURWITZ & THIBEAULT, LLP
                                ATTORNEYS AT LAW
                                 125 HIGH STREET
      OFFICE (617) 248-7000 BOSTON, MASSACHUSETTS 02110 FAX (617) 248-7100

                                                                    July 7, 2000
Matritech, Inc.
330 Nevada Street
Newton, MA  02460

        RE:   Registration Statement on Form S-3
              Relating to 2,450,000 Shares of Common Stock

Ladies and Gentlemen:

         We are counsel to Matritech, Inc., a Delaware corporation (the
"Company"), and have represented the Company in connection with the preparation
and filing of the Company's Form S-3 Registration Statement (the "Registration
Statement"), covering the sale to the public of up to 2,450,000 shares of the
Company's Common Stock, $.01 par value per share (the "Shares"). Terms not
otherwise defined herein shall have the meaning assigned to them in the
Registration Statement.

         We have reviewed the corporate proceedings taken by the Board of
Directors of the Company with respect to the authorization and issuance of the
Shares. We have also examined and relied upon originals or copies, certified or
otherwise authenticated to our satisfaction, of all corporate records,
documents, agreements or other instruments of the Company and have made all
investigations of law and have discussed with the Company's officers all
questions of fact that we have deemed necessary or appropriate.

         We are only members of the bar of the Commonwealth of Massachusetts and
are not expert in, and express no opinion regarding, the laws of any
jurisdiction other than the Commonwealth of Massachusetts, the General
Corporation Law of the State of Delaware and the United States of America.

         Based upon and subject to the foregoing, we are of the opinion that the
Shares are, or in the case of Shares issuable upon exercise of certain warrants,
when issued and paid for in accordance with the terms thereof, will be validly
issued, fully paid and nonassessable.

         We hereby consent to the filing of this opinion as Exhibit 5.1 to the
Registration Statement and to the reference to our firm in the Prospectus
contained in the Registration Statement under the caption "Legal Matters."

                                            Very truly yours,

                                            /s/ Testa, Hurwitz & Thibeault, LLP
                                            TESTA, HURWITZ & THIBEAULT, LLP