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                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                                WASHINGTON, D.C.

                                ----------------

                                  SCHEDULE 13G
                                 (Rule 13d-102)

           INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO
             RULES 13d-1(b)(c) AND (d) AND AMENDMENTS THERETO FILED
                           PURSUANT TO RULE 13d-2(b)

                     (Amendment No. __1___)(1)

                               Gartner Group, Inc.
                               ------------------
                                (Name of Issuer)

                              Class A Common Stock
                         ------------------------------
                         (Title of Class of Securities)

                                    366651107
                                  -------------
                                 (CUSIP Number)

                                December 31, 1999
             ------------------------------------------------------
             (Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule
13G is filed:

          [ ] Rule 13d-1(b)

          [ ] Rule 13d-1(c)

          [X] Rule 13d-1(d)

(1) The remainder of this cover page shall be filled out for a reporting
person's initial filing on this form with respect to the subject class of
securities, and for any subsequent amendment containing information which would
alter disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).
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                    (Continued on following page(s))

                           Page 1 of 7 Pages


SCHEDULE 13G CUSIP NO. 366651107 - ------------------- 1. NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. ABOVE PERSON IMS Health Incorporated 06-1506026 - ----------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) (b) - ----------------------------------------------------------- 3. SEC USE ONLY - ----------------------------------------------------------- 4. CITIZENSHIP OR PLACE OF ORGANIZATION Delaware - ----------------------------------------------------------- 5. SOLE VOTING POWER NUMBER OF 7,391,481 SHARES ----------------------------------------- BENEFICIALLY 6. SHARED VOTING POWER OWNED BY 117,376 EACH ----------------------------------------- REPORTING 7. SOLE DISPOSITIVE POWER PERSON 7,391,481 WITH ----------------------------------------- 8. SHARED DISPOSITIVE POWER 117,376 ----------------------------------------- 9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 7,391,481 - ----------------------------------------------------------- 10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* ( ) - ----------------------------------------------------------- 11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 9.7% - ----------------------------------------------------------- 12. TYPE OF REPORTING PERSON* CO - ----------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! Page 2 of 7 Pages

SCHEDULE 13G CUSIP NO. 366651107 - -------------------- 1. NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. ABOVE PERSON IMS Health Licensing Associates, L.P. 98-0137321 - ----------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) (b) - ----------------------------------------------------------- 3. SEC USE ONLY - ----------------------------------------------------------- 4. CITIZENSHIP OR PLACE OF ORGANIZATION Delaware - ----------------------------------------------------------- NUMBER OF 5. SOLE VOTING POWER SHARES -0- BENEFICIALLY ----------------------------------------- OWNED BY 6. SHARED VOTING POWER EACH 117,376 REPORTING ----------------------------------------- PERSON 7. SOLE DISPOSITIVE POWER WITH -0- ----------------------------------------- 8. SHARED DISPOSITIVE POWER 117,376 ----------------------------------------- 9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 117,376 - ----------------------------------------------------------- 10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* ( ) - ----------------------------------------------------------- 11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0.15% - ----------------------------------------------------------- 12. TYPE OF REPORTING PERSON* CO - ----------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! Page 3 of 7 Pages

ITEM 1 (a). NAME OF ISSUER Gartner Group, Inc. - ----------------------------------------------------------- ITEM 1 (b). ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES 56 Top Gallant Road, Stamford, Connecticut 06904-2212 - ----------------------------------------------------------- ITEM 2 (a). NAME OF PERSON FILING IMS Health Incorporated ("IMS HEALTH") and its subsidiary, IMS Health Licensing Associates, L.P. ("IMSHLA") - ---------------------------------------------------------- ITEM 2 (b). ADDRESS OF PRINCIPAL BUSINESS OFFICE The principal business office of IMS HEALTH is located at 200 Nyala Farms, Westport, Connecticut 06880. The principal business office of IMSHLA is located at Dorfplatz 4, 6330 CHAM Switzerland. - ----------------------------------------------------------- ITEM 2 (c). CITIZENSHIP IMS HEALTH is incorporated under the laws of the State of Delaware. IMSHLA is a limited partnership established under the laws of the State of Delaware. - ----------------------------------------------------------- ITEM 2 (d). TITLE OF CLASS OF SECURITIES Class A Common Stock - ----------------------------------------------------------- ITEM 2 (e). CUSIP NUMBER 366651107 - ----------------------------------------------------------- ITEM 3. Not Applicable - ----------------------------------------------------------- ITEM 4. OWNERSHIP The following information is provided as of December 31, 1999: (a) Amount Beneficially Owned IMS HEALTH is the owner of record and beneficially of 6,792,081 shares of Class A Common Stock and Warrants to purchase 599,400 shares of Class A Common Stock. IMSHLA is the owner of record and beneficially of 117,376 shares of Class A Common Stock. With an 84.52% interest in IMSHLA, IMS HEALTH may be deemed to be a beneficial owner of the shares held by it, for an aggregate beneficial ownership by IMS HEALTH of 7,508,857 shares. Page 4 of 7 Pages

(b) Percent of Class: IMS HEALTH - 9.7% (this percentage calculation assumes the conversion of the Warrant to purchase 599,400 shares of Common Stock) IMSHLA - 0.15% (c) NUMBER OF SHARES AS TO WHICH IMS HEALTH, Enterprises and IMSHLA HAVE: (i) sole power to vote or to direct the vote: IMS HEALTH - 7,391,481 (includes 599,400 shares issuable pursuant to the Warrant) IMSHLA - None (ii) shared power to vote or to direct the vote: IMS HEALTH - 117,376 IMSHLA - 117,376 (iii) sole power to dispose or to direct the disposition of: IMS HEALTH - 7,391,481 (includes 599,400 shares issuable pursuant to the Warrant) IMSHLA - None (iv) shared power to dispose or to direct the disposition of: IMS HEALTH - 117,376 IMSHLA - 117,376 ITEM 5. OWNERSHIP OF FIVE PERCENT OR LESS OF CLASS Not Applicable - ------------------------------------------------------------ ITEM 6. OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON Not applicable - ------------------------------------------------------------ Page 5 of 7 Pages

ITEM 7. IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH ACQUIRED THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING COMPANY Not applicable - ------------------------------------------------------------ ITEM 8. IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP Not applicable - ------------------------------------------------------------ ITEM 9. NOTICE OF DISSOLUTION OF GROUP Not applicable - ------------------------------------------------------------ ITEM 10. CERTIFICATION Not applicable - ------------------------------------------------------------ SIGNATURE - ---------- After reasonable inquiry and to the best of my knowledge and belief I certify that the information set forth in this statement is true, complete and correct. Dated: February 1, 2000 IMS HEALTH INCORPORATED By /s/ MATTHEW L. FRIEDMAN ------------------------------ Name: Matthew L. Friedman Title: Vice President and Treasurer IMS HEALTH LICENSING ASSOCIATES, L.P. By /s/ PETER ECSHER ------------------------------- Peter Ecsher, on behalf of the General Partner, IMS Pharminform Holding, AG Page 6 of 7 Pages

AGREEMENT Westport, CT February 1, 2000 IMS Health Incorporated ("IMS HEALTH") and IMS Health Licensing Associates, L.P.("IMSHLA")hereby agree to file a joint Schedule 13G under the Securities Exchange Act of 1934 (the "Act") in connection with their beneficial ownership of common stock issued by Gartner Group, Inc. IMS HEALTH and IMSHLA state they are each entitled to individually use Schedule 13G pursuant to Rule 13d-1 (d) of the Act. Each of IMS HEALTH and IMSHLA are responsible for the timely filing of the statement and any amendments thereto and for the completeness and accuracy of the information concerning each of them contained therein, but none is responsible for the completeness or accuracy of the information concerning the other. IMS HEALTH INCORPORATED By:/s/ MATTHEW L. FRIEDMAN ----------------------------- Name: Matthew L. Friedman Title: Vice President and Treasurer IMS HEALTH LICENSING ASSOCIATES, L.P. By /s/ PETER ECSHER ------------------------------- Peter Escher,on behalf of the General Partner, IMS Pharminform Holding, AG Page 7 of 7 Pages