<Page>

                                                                    EXHIBIT 99.1

     STATEMENT UNDER OATH OF PRINCIPAL EXECUTIVE OFFICER REGARDING FACTS AND
                 CIRCUMSTANCES RELATING TO EXCHANGE ACT FILINGS



I, David M. Thomas, state and attest that:

      (1)   To the best of my knowledge, based upon a review of the covered
            reports of IMS Health Incorporated, and, except as corrected or
            supplemented in a subsequent covered report:

                  o     no covered report contained an untrue statement of a
                        material fact as of the end of the period covered by
                        such report (or in the case of a report on Form 8-K or
                        definitive proxy materials, as of the date on which it
                        was filed); and

                  o     no covered report omitted to state a material fact
                        necessary to make the statements in the covered report,
                        in light of the circumstances under which they were
                        made, not misleading as of the end of the period covered
                        by such report (or in the case of a report on Form 8-K
                        or definitive proxy materials, as of the date on which
                        it was filed).

      (2)   I have reviewed the contents of this statement with the IMS Health
            Incorporated's audit committee.

      (3)   In this statement under oath, each of the following, if filed on or
            before the date of this statement, is a "covered report":

                  o     Annual Report on Form 10-K for the year ended December
                        31, 2001 of IMS Health Incorporated;

                  o     all reports on Form 10-Q, all reports on Form 8-K and
                        all definitive proxy materials of IMS Health
                        Incorporated filed with the Commission subsequent to the
                        filing of the Form 10-K identified above; and

                  o     any amendments to any of the foregoing.



 /s/ David M. Thomas                        Subscribed and sworn to before
- ---------------------------                 me this 12th day of August 2002.
David M. Thomas
                                            /s/ Robin Y. Nance
                                            -------------------------
August 12, 2002                             Robin Y. Nance
                                            Notary Public

                                            My Commission Expires: 10/31/03