Exhibit 5

                       [Brown, Rudnick, Freed & Gesmer]

                              September 11, 1996


Hologic, Inc.
590 Lincoln Street
Waltham, MA 02154

RE: Registration Statement on Form S-8
    ----------------------------------

Ladies and Gentlemen:

     We are general counsel to Hologic, Inc., a Delaware corporation (the
"Company").  We have been asked to deliver this opinion in connection with the
preparation and filing with the Securities and Exchange Commission under the
Securities Act of 1933, as amended (the "Act"), of a Registration Statement on
Form S-8 (the "Registration Statement") relating to 1,150,000 shares of the
Company's Common Stock, $.01 par value (the "Shares") and 3,326,750 Rights, as
defined below.  The Rights are issuable pursuant to that certain Rights
Agreement, dated as of December 22, 1992, as amended by Amendment No. 1 dated
December 14, 1995 (the "Rights Agreement"), providing, in effect, for the
delivery of a right (a "Right"), along with each share of Common Stock issued by
the Company.

     Of the Shares, (i) 50,000 are issuable upon exercise of options granted or
to be granted pursuant to the Company's Amended and Restated 1990 Nonemployee
Director Stock Option Plan (the "Directors Plan") and (ii) 1,100,000 are
issuable upon exercise of options granted or to be granted pursuant to the
Company's 1995 Combination Stock Option Plan (the "1995 Plan").

     Of the Rights, (i) 200,000 are issuable upon exercise of options granted or
to be granted pursuant to the Directors Plan, (ii) 1,100,000 are issuable upon
exercise of options granted or to be granted pursuant to the 1995 Plan, (iii)
200,000 are issuable upon exercise of options granted or to be granted pursuant
to the Company's 1995 Stock Purchase Plan (the "Purchase Plan"), (vi) 1,726,750
are issuable upon exercise of options granted or to be granted under the
Company's 1986 Combination Stock Option Plan (the "1986 Plan"), and (v) 100,000
are issuable pursuant to the Company's Savings and Investment Plan (the "Savings
Plan"). The Directors Plan, the 1995 Plan, the Purchase Plan, the 1986 Plan and
the Savings Plan are hereinafter referred to collectively as the Plans.

     In connection with this opinion, we have examined and are familiar with
originals or copies, certified or otherwise identified to our satisfaction, of
the following documents (collectively, the "Documents"):

     1. A copy of the Certificate of Incorporation of the Company as in effect
        on the date hereof;

 
Hologic, Inc.
September 11, 1995
Page 2


       2. A copy of the Bylaws of the Company as in effect on the date hereof;

       3. The corporate records of the Company relating to the proceedings of
          stockholders and directors of the Company;
  
       4. Each of the Plans;

       5. The Rights Agreement; and

       6. The Registration Statement.

       In giving our opinion, we have relied as to matters of fact upon
certificates of officers of the Company.  For purposes of this opinion we have
assumed without any investigation (1) the legal capacity of each natural person
and (2) the genuineness of each signature, the completeness of each document
submitted to us as an original and the conformity with the original of each
document submitted to us as a copy.

       Our opinion hereafter expressed is based solely upon (1) our review of
the Documents, (2) discussions with certain officers of the Company with respect
to the Documents, (3) discussions with those of our attorneys who have devoted
substantive attention to the matters contained herein and (4) such review of
published sources of law as we have deemed necessary.

     Based upon and subject to the foregoing, we are of the opinion that the
Shares have been duly authorized and, when issued in accordance with the terms
of the applicable Plan, the Shares will be validly issued, fully paid and
nonassessable.    The Rights have been duly authorized and, when issued in
accordance with the terms of the Rights Agreement, 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 wherever it appears in
the Registration Statement.

                                  Very truly yours,
                             
                                  BROWN, RUDNICK, FREED & GESMER, P.C.
                                  By:  Brown, Rudnick, Freed & Gesmer, a partner
                             
                                  By: /s/ Philip J. Flink
                                      ------------------------------------------
                                      Philip J. Flink, a Member
                                      hereunto duly authorized

PJF/LML