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

Each of the undersigned, in his capacity as an officer of La Jolla
Pharmaceutical Company (the "Registrant"), hereby certifies, for purposes of 18
U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley
Act of 2002, that:

         -    the annual report of the Registrant on Form 10-K for the year
              ended December 31, 2002 ("the Report"), which accompanies this
              certification, fully complies with the requirements of Section
              13(a) or 15(d) of the Securities and Exchange Act of 1934; and

         -    the information contained in the Report fairly presents, in all
              material respects, the financial condition of the Registrant at
              the end of such year and the results of operations of the
              Registrant of such year.

Date:  March 27, 2003

                                           /s/ Steven B. Engle
                                           ------------------------------------
                                           Steven B. Engle
                                           Chairman and Chief Executive Officer

                                           /s/ David Duncan, Jr.
                                           ------------------------------------
                                           David Duncan, Jr.
                                           Chief Financial Officer

Note:  A signed original of this written statement required by Section 906 has
       been provided to La Jolla Pharmaceutical Company and will be retained by
       La Jolla Pharmaceutical Company and furnished to the Securities and
       Exchange Commission or its staff upon request.