EXHIBIT 99.10

                            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 Annual Report of ImClone Systems Incorporated (the
"Company") on Form 10-K for the period ended December 31, 2002 as filed with the
Securities and Exchange Commission on the date hereof (the "Report"), I, Michael
J. Howerton, Vice President, Finance and Business Development, acting Chief
Financial Officer and Secretary 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:

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

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

                                             /s/ Michael J. Howerton
                                             ----------------------------------
                                             Michael J. Howerton
                                             Acting Chief Financial Officer
June 23, 2003