EXHIBIT 10.1
                              AMENDMENT NO. 2 TO
                             ASSIGNMENT AGREEMENT


          This Amendment No. 2 to Assignment Agreement  (this "Amendment"),
dated as of September 30, 1997, amends that certain Assignment Agreement, dated
as of April 13, 1994 (the "Assignment Agreement"), among Zonagen, Inc., a
Delaware corporation ("Zonagen"), Gamogen, Inc., a New York corporation
("Gamogen"), and Dr. Adrian Zorgniotti ("Zorgniotti"), as amended by Conditional
Amendment No. 1 thereto dated as of January 24, 1997 (the "Conditional
Amendment").  Capitalized terms used without definition in this Amendment shall
have the meanings ascribed thereto in the Assignment Agreement and the
Conditional Amendment.

                                  WITNESSETH
                                  ----------


          WHEREAS, Gamogen and Zorgniotti assigned certain technology (referred
to in the Assignment Agreement as the "Subject Technology") to Zonagen pursuant
to the Assignment Agreement; and

          WHEREAS, Zonagen agreed in the Assignment Agreement to pay certain
royalties to Gamogen with respect to its sales of any Royalty-Bearing Product;
and

          WHEREAS, Gamogen and Zonagen amended the Assignment Agreement in the
Conditional Amendment to provide Zonagen with the option to terminate its
obligations with respect to royalties on Royalty-Bearing Products in exchange
for payments by Zonagen;

          WHEREAS, Gamogen and Zonagen desire to enter this Amendment to
evidence (i) the exercise of such option by Zonagen, (ii) the payment of the
Option Price (as reduced hereby) by Zonagen and (iii) the amendment of the
Assignment Agreement to terminate Zonagen's obligations with respect to
royalties on Royalty-Bearing Products;

          NOW, THEREFORE, in consideration of the foregoing and the mutual
covenants and promises contained in this Amendment, the parties hereto agree as
follows:

          1.  Exercise of Option. Concurrently with the execution of this
Amendment (which constitutes notice of the exercise of the Option), Zonagen has
delivered $558,000 in cash to Gamogen in full payment of the Option Price, which
amount reflects (i) a credit in an amount equal to the $150,000 in Maintenance
Payments previously made by Zonagen and (ii) a reduction of $42,000 in the
amount of the Option Price in consideration for Zonagen's agreement to exercise
the Option as of the date of this Amendment.

          2.  Amendment of Assignment Agreement. Section 2.1(b) of the
Assignment Agreement is hereby amended by deleting subsection (iii) thereof in
its entirety. Article II of the Assignment Agreement is hereby further amended
by deleting Section 2.3 thereof in its entirety. Without limiting the foregoing,
this Amendment shall terminate (x) any and all obligations of Zonagen with
respect to (i) the payment of royalties on Royalty-Bearing Products and (ii)
obtaining regulatory approval for and marketing Royalty-Bearing Products, and
(y) any and all rights whatsoever of Gamogen under the Assignment Agreement.

          3.  Representations and Warranties.   Each party hereto represents
and warrants to the other party as follows:

 
          (a) It is a corporation duly organized, validly existing, and in good
     standing under the laws of jurisdiction of its incorporation, with the
     requisite power to enter into and perform its obligations under this
     Amendment in accordance with terms hereof.

          (b) It has the full right, power and authority to execute and deliver
     this Amendment and to perform the terms hereof.  It has taken all required
     corporate actions to approve and adopt this Amendment.   This Amendment has
     been duly authorized by all necessary corporate action, and upon execution
     and delivery thereof will be its valid and binding agreement enforceable
     against it in accordance with the terms hereof, subject as to enforcement
     to bankruptcy, insolvency and other laws of general applicability relating
     to or affecting creditors' rights and to general principles of equity.

          (c) Its execution and delivery of this Amendment and the consummation
     of the transactions required hereby (i) do not and will not violate or
     conflict with any statute, regulation, judgment, order, writ, decree, or
     injunction, currently applicable to it, any of its subsidiaries or any of
     their respective property or assets, and (ii) will not violate or conflict
     with any provision of its articles of incorporation or bylaws or any
     existing mortgage, indenture, contract, licensing agreement, financing
     statement, or other agreement binding on it or any of its subsidiaries.

          (d) No consent or approval of its stockholders or any third party is
     required to be obtained by it in connection with the execution and delivery
     of this Amendment or the performance of the transactions contemplated
     hereby.  No material contract or agreement to which it is a party restricts
     its ability to fulfill its obligations and responsibilities under this
     Amendment or to carry out the activities contemplated herein.

          4.   No Other Changes.  The Assignment Agreement shall continue to be
in full force and effect in accordance with the terms thereof, except to the
extent such terms are amended by this Amendment.

          IN WITNESS WHEREOF, the parties have executed this Amendment as of the
date first set forth above.


                                ZONAGEN, INC.

                                By: /s/ LOUIS PLOTH, JR.
                                   ----------------------------
                                    Louis Ploth, Jr.
                                    Vice President and Chief Financial Officer


                                GAMOGEN, INC.

                                By: /s/ JESSE A. GARRINGER
                                   ----------------------------
                                    Jesse A. Garringer
                                    Executive Vice President


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