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                                                                    EXHIBIT 99.3

                    CERTIFICATION OF CHIEF EXECUTIVE OFFICER
            PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002
        (SUBSECTIONS (a) AND (b) OF SECTION 1350, CHAPTER 63 OF TITLE 18,
                              UNITED STATES CODE)



      Pursuant to section 906 of the Sarbanes-Oxley Act of 2002 (subsections (a)
and (b) of section 1350, chapter 63 of title 18, United States Code), the
undersigned officer of IMS Health Incorporated, a Delaware corporation (the
"Company"), does hereby certify that:

      The Quarterly Report on Form 10-Q for the quarter ended June 30, 2002 (the
      "Form 10-Q") of the Company fully complies with the requirements of
      section 13(a) or 15(d), as applicable, of the Securities Exchange Act of
      1934 and information contained in the Form 10-Q fairly presents, in all
      material respects, the financial condition and results of operations of
      the Company.


Dated: August 12, 2002              /s/ David M. Thomas
                                    -------------------
                                    David M. Thomas
                                    Chairman, Chief Executive Officer and
                                         President, IMS Health Incorporated




The foregoing certification is being furnished solely pursuant to section 906 of
the Sarbanes-Oxley Act of 2002 (subsections (a) and (b) of section 1350, chapter
63 of title 18, United States Code) and is not being filed as part of the Form
10-Q or as a separate disclosure document.