UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549



                                    FORM 8-K

             CURRENT REPORT FILED PURSUANT TO SECTION 13 OR 15(d) OF
                       THE SECURITIES EXCHANGE ACT OF 1934


                                 DATE OF REPORT
                (DATE OF EARLIEST EVENT REPORTED): MARCH 30, 2004


                                  ZONAGEN, INC.
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

<Table>
                                                                       
           DELAWARE                              0-21198                             76-0233274
(STATE OR OTHER JURISDICTION OF          (COMMISSION FILE NUMBER)        (I.R.S. EMPLOYER IDENTIFICATION NO.)
 INCORPORATION OR ORGANIZATION)
</Table>



                        2408 TIMBERLOCH PLACE, SUITE B-10
                           THE WOODLANDS, TEXAS 77380
                              (ADDRESS OF PRINCIPAL
                                EXECUTIVE OFFICES
                                  AND ZIP CODE)

                                 (281) 719-3400
                         (REGISTRANT'S TELEPHONE NUMBER,
                              INCLUDING AREA CODE)




ITEM 7. FINANCIAL STATEMENTS AND EXHIBITS

        c.  Exhibits

        Exhibit
        Number            Description
        -------           -----------
         99.1             Press Release dated March 30, 2004.

ITEM 12. RESULTS OF OPERATIONS AND FINANCIAL CONDITION

         On March 30, 2004, Zonagen, Inc. (the "Company") announced in a press
release its financial results for the three months and year ended December 31,
2003. A copy of the Company's press release is attached hereto as Exhibit 99.1.
The press release is incorporated by reference herein and the foregoing
description of the press release is qualified in its entirety by reference to
the attached exhibit.

         The information in this report, including the Exhibit, is being
furnished and shall not be deemed to be "filed" for purposes of Section 18 of
the Securities Exchange Act of 1934, as amended, or otherwise subject to the
liabilities of that Section. In addition, the information in this report,
including the Exhibit, shall not be incorporated by reference into the filings
of the Company under the Securities Act of 1933, as amended, or the Securities
Exchange Act of 1934, as amended, except as shall be expressly set forth by
specific reference in such filing.







                                   SIGNATURES

         Pursuant to the requirements of the Securities Exchange Act of 1934,
the Registrant has duly caused this report to be signed on its behalf by the
undersigned hereunto duly authorized.


                                     ZONAGEN, INC.

Date: April 1, 2004.

                                     By: /s/ Louis Ploth, Jr.
                                        ----------------------------------------
                                        Louis Ploth, Jr.
                                        Vice President, Business Development and
                                        Chief Financial Officer





                                  EXHIBIT INDEX


Exhibit
Number         Description
- -------        -----------
 99.1          Press Release dated March 30, 2004.