EXHIBIT 99.1


                            CERTIFICATION PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002


         In connection with the Quarterly Report of Zonagen, Inc. (the
"Company") on Form 10-Q for the quarter ended March 31, 2003 as filed with the
Securities and Exchange Commission on the date hereof (the "Report"), I, Joseph
S. Podolski, President and Chief Executive Officer of the Company, certify,
pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the
Sarbanes-Oxley Act of 2002, that:

1. The Report fully complies with the requirements of section 13(a) or 15(d) of
the Securities Exchange Act of 1934; and

2. The information contained in the Report fairly presents, in all material
respects, the financial condition and results of operations of the Company.

Dated:  May 13, 2003                       By: /s/ Joseph S. Podolski
                                              -------------------------
                                              Joseph S. Podolski
                                              President and
                                              Chief Executive Officer
                                              Zonagen, Inc.


A signed original of the written statement required by Section 906 has been
provided to Zonagen and will be retained by Zonagen and furnished to the
Securities and Exchange Commission and its staff upon request.