[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 297,517 shares of the Company's Common Stock, $.01 par value (the "Shares") and 297,517 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 and Rights, (i) 22,370 are issuable upon exercise of options granted pursuant to the FluoroScan Imaging Systems, Inc. 1994 Amended and Restated Stock Incentive Plan, (ii) 124,742 are issuable upon exercise of options granted pursuant to the FluoroScan Imaging Systems, Inc. 1995 Stock Incentive Plan and (iii) 150,405 are issuable upon exercise of options granted pursuant to the FluoroScan Imaging Systems, Inc. 1994 Directors Stock Option Plan. The aforementioned plans (collectively, the "Plans") were assumed by the Company upon the merger of FluoroScan Imaging Systems, Inc. ("FluoroScan"), with and into a wholly-owned subsidiary of the Company on August 29, 1996 pursuant to an Agreement and Plan of Merger dated July 18, 1996 among the Company, FluoroScan and the Company's subsidiary (the "Merger Agreement"). 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; 2. A copy of the Bylaws of the Company as in effect on the date hereof; Hologic, Inc September 11, 1996 Page 2 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; 6. The Merger Agreement; and 7. 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