<PAGE>   1
    As filed with the Securities and Exchange Commission on February 16, 2000

                                                  Registration No. 333-
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933



                               GARTNER GROUP, INC.
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

                     Delaware                        04-3099750
          (STATE OR OTHER JURISDICTION OF         (I.R.S. EMPLOYER
          INCORPORATION OR ORGANIZATION)         IDENTIFICATION NO.)


                 P.O. Box 10212
               56 Top Gallant Road
              Stamford, Connecticut                  06904-2212
    (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)         (ZIP CODE)



                   Gartner Group, Inc. 1999 Stock Option Plan
                            (FULL TITLE OF THE PLAN)



                               Regina M. Paolillo
                        Executive Vice President-Finance
                 and Administration and Chief Financial Officer
                               Gartner Group, Inc.
                               56 Top Gallant Road
                                 P.O. Box 10212
                        Stamford, Connecticut 06904-2212
                     (NAME AND ADDRESS OF AGENT FOR SERVICE)


                                 (203) 316-1111
          (TELEPHONE NUMBER, INCLUDING AREA CODE, OF AGENT FOR SERVICE)


                                    Copy to:

                            Michael J. Palmieri, Esq.
                              Shipman & Goodwin LLP
                               One Landmark Square
                           Stamford, Connecticut 06901
                                 (203) 324-8100
<PAGE>   2
                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
                                                            PROPOSED             PROPOSED
                                       AMOUNT               MAXIMUM               MAXIMUM
     TITLE OF SECURITIES               TO BE             OFFERING PRICE          AGGREGATE           AMOUNT OF
       TO BE REGISTERED              REGISTERED           PER UNIT (1)        OFFERING PRICE      REGISTRATION FEE
     -------------------             ----------          --------------       --------------      ----------------
<S>                                  <C>                 <C>                  <C>                 <C>
Class A Common Stock, par
value $.0.0005.............          20,000,000             $14.16               $283,200,000        $74,765
</TABLE>

(1)   Estimated solely for the purpose of calculating the registration fee
      pursuant to Rule 457(h) under the Securities Act of 1933 based on the
      average of the high and low prices reported on the New York Stock Exchange
      on February 9, 2000.
<PAGE>   3
                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

     The Section 10(a) prospectus being delivered by Gartner Group, Inc. (the
"Company") to participants in the Company's 1999 Stock Option Plan (the "Plan"),
as required by Rule 428 under the Securities Act of 1933, as amended (the
"Securities Act"), has been prepared in accordance with the requirements of Form
S-8 and relates to shares of Class A Common Stock, par value $0.0005 per share,
issued or reserved for issuance pursuant to awards granted under the Plan. The
information with respect to awards granted under the Plan required in the
Section 10(a) prospectus is included in documents being maintained and delivered
by the Company as required by Rule 428 under the Securities Act. The Company
shall provide to participants a written statement advising them of the
availability without charge, upon written or oral request, of documents
incorporated by reference herein, as is required by Item 2 of Part I of Form
S-8.
<PAGE>   4
                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.    INCORPORATION OF DOCUMENTS BY REFERENCE.

     The following documents are hereby incorporated by reference in this
registration statement:

           (a) The Company's Annual Report on Form 10-K for the year ended
September 30, 1999;

           (b) The Company's Quarterly Report on Form 10-Q for the quarter ended
December 31, 1999;

           (c) The Company's Current Report on Form 8-K dated January 3, 2000;
and

           (d The description of the Company's Class A and Class B Common Stock,
contained in its registration statement on Form 8-A filed on July 7, 1999 and in
its Form 8-K dated January 3, 2000, and any amendment or report filed for the
purpose of updating such description.

     All documents subsequently filed by the Company pursuant to Sections 13(a),
13(c), 14 and 15(d) of the Securities Exchange Act of 1934, as amended (the
"Exchange Act"), on or after the date of this registration statement and prior
to the filing of a post-effective amendment which indicates that all securities
offered hereby have been sold or which deregisters all such securities then
remaining unsold, shall be deemed to be incorporated by reference in this
registration statement and to be part thereof from the date of filing of such
documents. Any statement contained in a document incorporated or deemed to be
incorporated by reference in this registration statement shall be deemed to be
modified or superseded for purposes of this registration statement to the extent
that a statement contained herein or in any other subsequently filed document
which also is or is deemed to be incorporated by reference herein modifies or
supersedes such statement. Any such statement so modified or superseded shall
not be deemed, except as so modified or superseded, to constitute a part of this
registration statement.

ITEM 4.    DESCRIPTION OF SECURITIES.

     This Item is not applicable.

ITEM 5.    INTERESTS OF NAMED EXPERTS AND COUNSEL.

     This Item is not applicable.

ITEM 6.    INDEMNIFICATION OF DIRECTORS AND OFFICERS.

     Section 145 of the Delaware General Corporation Law ("Delaware Law")
provides that a corporation may indemnify a director, officer, employee or agent
made a party to an action by reason of the fact that he was a director, officer,
employee or agent of the corporation, or was


                                      II-1
<PAGE>   5
serving at the request of the corporation, against expenses actually and
reasonably incurred, including attorneys' fees, in connection with such action,
if he acted in good faith and in a manner he reasonably believed to be in, or
not opposed to, the best interests of the corporation and, with respect to any
criminal action, had no reasonable cause to believe his conduct was unlawful.

     The Company's Certificate of Incorporation limits, to the maximum extent
permitted by Delaware Law, the personal liability of a director to the Company
or its stockholders for monetary damages for breach of fiduciary duty as a
director. The Company's Bylaws provide that the Company shall indemnify its
officers and directors to the fullest extent permitted by Delaware Law against
all expense, liability and loss, including attorneys' fees, actually and
reasonably incurred and may purchase and maintain insurance against any
liability asserted and incurred by reason of serving as such, whether or not the
Company has the power to indemnify against such liability. The Company has
entered into indemnification agreements with its officers and directors
containing provisions which are in some respects broader than the specific
indemnification provisions contained in Delaware Law and which require that, to
the extent the Company maintains liability insurance applicable to officers or
directors, each officer and director shall be covered by such policies to the
same extent as are accorded the most favorably insured of the Company's officers
or directors, as the case may be.

     Insofar as indemnification for liabilities arising under the Securities Act
may be permitted to directors, officers, or persons controlling the Company
pursuant to the foregoing provisions and agreements, the Company has been
informed that in the opinion of the Securities and Exchange Commission, such
indemnification is against public policy as expressed in the Securities Act and
is therefore unenforceable.

ITEM 7.    EXEMPTION FROM REGISTRATION CLAIMED.

     This Item is not applicable.

ITEM 8.    EXHIBITS.

Exhibit No.                         Description
-----------                         -----------

  4.1             Amended and Restated Certificate of Incorporation of the
                  Company (filed as Exhibit A to the Company's Registration
                  Statement on Form 8-A (File No. 1-14443) as filed on July 7,
                  1999 and incorporated herein by reference).

  4.2(a)          Bylaws of the Company (filed as Exhibit B(1) to the Company's
                  Registration Statement on Form 8-A (File No. 1-14443) as filed
                  on July 7, 1999 and incorporated herein by reference).

  4.2(b)          Amendment to Bylaws of the Company (filed as Exhibit B(2) to
                  the Company's Registration Statement on Form 8-A (File No.
                  1-14443) as filed on July 7, 1999 and incorporated herein by
                  reference).

  4.3             Form of Certificate for Common Stock, Class A (filed as
                  Exhibit 4.2 to the


                                      II-2
<PAGE>   6
                  Company's Registration Statement on Form S-1 (File No.
                  33-67576) and incorporated herein by reference).

      5.1*        Opinion of Shipman & Goodwin LLP as to the legality of the
                  securities being registered.

     23.1*        Consent of Shipman & Goodwin LLP (included in Exhibit 5.1).

     23.2*        Consent of KPMG LLP.

     24.1*        Power of Attorney (included in the signature page of this
                  registration statement).

     99.1*        Gartner Group, Inc. 1999 Stock Option Plan.


*Filed herewith.


ITEM 9.    UNDERTAKINGS.

     (a)   The undersigned registrant hereby undertakes:

           (1) To file, during any period in which offers or sales are being
made, a post-effective amendment to this registration statement to include any
material information with respect to the plan of distribution not previously
disclosed in the registration statement or any material change to such
information in the registration statement.

           (2) That, for the purpose of determining any liability under the
Securities Act, each such post-effective amendment shall be deemed to be a new
registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

           (3) To remove from registration by means of a post-effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

     (b)   The undersigned registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act, each filing of the
registrant's annual report pursuant to Section 13 or Section 15(d) of the
Exchange Act (and, where applicable, each filing of an employee benefit plan's
annual report pursuant to Section 15(d) of the Exchange Act) that is
incorporated by reference in the registration statement shall be deemed to be a
new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

     (c)   Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling persons
of the registrant pursuant to the foregoing provisions, or otherwise, the
registrant has been advised that in the opinion of the Securities and Exchange
Commission such indemnification is against public policy as expressed in the
Securities Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
registrant of expenses incurred or paid by a director, officer or controlling
person of the registrant in the successful defense of any action, suit


                                      II-3
<PAGE>   7
or proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Securities
Act and will be governed by the final adjudication of such issue.


                                      II-4
<PAGE>   8
                                   SIGNATURES

     Pursuant to requirements of the Securities Act of 1933, the registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this registration
statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Stamford, State of Connecticut on February 15, 2000.

                                  GARTNER GROUP, INC.


                                  By: /s/ MICHAEL D. FLEISHER
                                      -------------------------------------
                                      Michael D. Fleisher
                                      President and Chief Executive Officer



                                POWER OF ATTORNEY

     Know All Persons by These Presents, that each person whose signature
appears below constitutes and appoints Michael D. Fleisher and Regina M.
Paolillo and each of them acting individually, as his or her true and lawful
attorneys-in-fact and agents, with full power of substitution and resubstitution
for him or her and in his or her name, place and stead, in any and all
capacities to sign any and all amendments (including post-effective amendments)
to this registration statement, and to file same, with all exhibits thereto, and
other documents in connection therewith with the Securities and Exchange
Commission, with full power and authority to do and perform each and every act
and thing requisite or necessary to be done in and about the premises, as fully
to all intents and purposes as he or she might or could do in person, hereby
ratifying and confirming all that said attorneys-in-fact and agents or any of
them, of their or his substitute or substitutes, may lawfully do or cause to be
done by virtue hereof.



     Pursuant to the requirements of the Securities Act of 1933, this
registration statement has been signed by the following persons in the
capacities and on the dates indicated.

<TABLE>
<CAPTION>
          SIGNATURE                                 TITLE                               DATE
          ---------                                 -----                               ----
<S>                                    <C>                                        <C>
/s/ MANUEL A . FERNANDEZ               Director, Chairman of the Board            February 15, 2000
--------------------------------
  Manuel A. Fernandez

/s/MICHAEL D. FLEISHER                 Director, President and Chief              February 15, 2000
--------------------------------       Executive Officer (Principal
  Michael D. Fleisher                  Executive Officer)

/s/ REGINA M. PAOLILLO                 Executive Vice President Finance and       February 15, 2000
--------------------------------       Administration and Chief Financial
  Regina M. Paolillo                   Officer
                                       (Principal Financial and Accounting
                                       Officer)

/s/ANNE SUTHERLAND FUCHS               Director                                   February 15, 2000
--------------------------------
  Anne Sutherland Fuchs

    /s/ WILLIAM O. GRABE               Director                                   February 15, 2000
--------------------------------
  William O. Grabe
</TABLE>


                                      II-5
<PAGE>   9
<TABLE>
<S>                                    <C>                                        <C>
      /s/ MAX D. HOPPER                Director                                   February 15, 2000
--------------------------------
  Max D. Hopper

   /s/ JOHN P. IMLAY, JR.              Director                                   February 15, 2000
--------------------------------
  John P. Imlay, Jr.

   /s/ CHARLES B. MCQUADE              Director                                   February 15, 2000
--------------------------------
  Charles B. McQuade

   /s/ STEPHEN G. PAGLIUCA             Director                                   February 15, 2000
--------------------------------
  Stephen G. Pagliuca

      /s/ KENNETH ROMAN                Director                                   February 15, 2000
--------------------------------
  Kenneth Roman

     /s/ DENNIS G. SISCO               Director                                   February 15, 2000
--------------------------------
  Dennis G. Sisco
</TABLE>


                                      II-6
<PAGE>   10
                                  EXHIBIT INDEX

Exhibit No.                                 Description
-----------                                 -----------



    4.1          Amended and Restated Certificate of Incorporation of the
                 Company (filed as Exhibit A to the Company's Registration
                 Statement on Form 8-A (File No. 1-14443) as filed on July 7,
                 1999 and incorporated herein by reference).

    4.2(a)       Bylaws of the Company (filed as Exhibit B(1) to the
                 Company's Registration Statement on Form 8-A (File No.
                 1-14443) as filed on July 7, 1999 and incorporated herein by
                 reference).

    4.2(b)       Amendment to Bylaws of the Company (filed as Exhibit B(2) to
                 the Company's Registration Statement on Form 8-A (File No.
                 1-14443) as filed on July 7, 1999 and incorporated herein by
                 reference).

    4.3          Form of Certificate for Common Stock, Class A (filed as Exhibit
                 4.2 to the Company's Registration Statement on Form S-1 (File
                 No. 33-67576) and incorporated herein by reference).

    5.1*         Opinion of Shipman & Goodwin LLP as to the legality of the
                 securities being registered.

   23.1*         Consent of Shipman & Goodwin LLP (included in Exhibit 5.1).

   23.2*         Consent of KPMG LLP.

   24.1*         Power of Attorney (included in the signature page of this
                 registration statement).

   99.1*         Gartner Group, Inc. 1999 Stock Option Plan.


*Filed herewith.
[{"type": "S-8", "sequence": "1", "description": "GARTNER GROUP, INC.", "secsgml_size_bytes": 19434}]
{"company-data": {"conformed-name": "GARTNER GROUP INC", "cik": "0000749251", "assigned-sic": "8741", "irs-number": "043099750", "state-of-incorporation": "DE", "fiscal-year-end": "0930"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-30546", "film-number": "547638"}, "business-address": {"street1": "56 TOP GALLANT RD", "street2": "P O BOX 10212", "city": "STAMFORD", "state": "CT", "zip": "06904-2212", "phone": "2039640096"}}
1
    As filed with the Securities and Exchange Commission on February 16, 2000

                                                  Registration No. 333-
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                               GARTNER GROUP, INC.
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

                     Delaware                        04-3099750
          (STATE OR OTHER JURISDICTION OF         (I.R.S. EMPLOYER
          INCORPORATION OR ORGANIZATION)         IDENTIFICATION NO.)

                 P.O. Box 10212
               56 Top Gallant Road
              Stamford, Connecticut                  06904-2212
    (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)         (ZIP CODE)

                   Gartner Group, Inc. 1999 Stock Option Plan
                            (FULL TITLE OF THE PLAN)

                               Regina M. Paolillo
                        Executive Vice President-Finance
                 and Administration and Chief Financial Officer
                               Gartner Group, Inc.
                               56 Top Gallant Road
                                 P.O. Box 10212
                        Stamford, Connecticut 06904-2212
                     (NAME AND ADDRESS OF AGENT FOR SERVICE)

                                 (203) 316-1111
          (TELEPHONE NUMBER, INCLUDING AREA CODE, OF AGENT FOR SERVICE)

                                    Copy to:

                            Michael J. Palmieri, Esq.
                              Shipman & Goodwin LLP
                               One Landmark Square
                           Stamford, Connecticut 06901
                                 (203) 324-8100
2
                         CALCULATION OF REGISTRATION FEE
PROPOSED             PROPOSED
                                       AMOUNT               MAXIMUM               MAXIMUM
     TITLE OF SECURITIES               TO BE             OFFERING PRICE          AGGREGATE           AMOUNT OF
       TO BE REGISTERED              REGISTERED           PER UNIT (1)        OFFERING PRICE      REGISTRATION FEE
     -------------------             ----------          --------------       --------------      ----------------
Class A Common Stock, par
value $.0.0005.............          20,000,000             $14.16               $283,200,000        $74,765
(1)   Estimated solely for the purpose of calculating the registration fee
      pursuant to Rule 457(h) under the Securities Act of 1933 based on the
      average of the high and low prices reported on the New York Stock Exchange
      on February 9, 2000.
3
                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

     The Section 10(a) prospectus being delivered by Gartner Group, Inc. (the
"Company") to participants in the Company's 1999 Stock Option Plan (the "Plan"),
as required by Rule 428 under the Securities Act of 1933, as amended (the
"Securities Act"), has been prepared in accordance with the requirements of Form
S-8 and relates to shares of Class A Common Stock, par value $0.0005 per share,
issued or reserved for issuance pursuant to awards granted under the Plan. The
information with respect to awards granted under the Plan required in the
Section 10(a) prospectus is included in documents being maintained and delivered
by the Company as required by Rule 428 under the Securities Act. The Company
shall provide to participants a written statement advising them of the
availability without charge, upon written or oral request, of documents
incorporated by reference herein, as is required by Item 2 of Part I of Form
S-8.
4
                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.    INCORPORATION OF DOCUMENTS BY REFERENCE.

     The following documents are hereby incorporated by reference in this
registration statement:

           (a) The Company's Annual Report on Form 10-K for the year ended
September 30, 1999;

           (b) The Company's Quarterly Report on Form 10-Q for the quarter ended
December 31, 1999;

           (c) The Company's Current Report on Form 8-K dated January 3, 2000;
and

           (d The description of the Company's Class A and Class B Common Stock,
contained in its registration statement on Form 8-A filed on July 7, 1999 and in
its Form 8-K dated January 3, 2000, and any amendment or report filed for the
purpose of updating such description.

     All documents subsequently filed by the Company pursuant to Sections 13(a),
13(c), 14 and 15(d) of the Securities Exchange Act of 1934, as amended (the
"Exchange Act"), on or after the date of this registration statement and prior
to the filing of a post-effective amendment which indicates that all securities
offered hereby have been sold or which deregisters all such securities then
remaining unsold, shall be deemed to be incorporated by reference in this
registration statement and to be part thereof from the date of filing of such
documents. Any statement contained in a document incorporated or deemed to be
incorporated by reference in this registration statement shall be deemed to be
modified or superseded for purposes of this registration statement to the extent
that a statement contained herein or in any other subsequently filed document
which also is or is deemed to be incorporated by reference herein modifies or
supersedes such statement. Any such statement so modified or superseded shall
not be deemed, except as so modified or superseded, to constitute a part of this
registration statement.

ITEM 4.    DESCRIPTION OF SECURITIES.

     This Item is not applicable.

ITEM 5.    INTERESTS OF NAMED EXPERTS AND COUNSEL.

     This Item is not applicable.

ITEM 6.    INDEMNIFICATION OF DIRECTORS AND OFFICERS.

     Section 145 of the Delaware General Corporation Law ("Delaware Law")
provides that a corporation may indemnify a director, officer, employee or agent
made a party to an action by reason of the fact that he was a director, officer,
employee or agent of the corporation, or was

                                      II-1
5
serving at the request of the corporation, against expenses actually and
reasonably incurred, including attorneys' fees, in connection with such action,
if he acted in good faith and in a manner he reasonably believed to be in, or
not opposed to, the best interests of the corporation and, with respect to any
criminal action, had no reasonable cause to believe his conduct was unlawful.

     The Company's Certificate of Incorporation limits, to the maximum extent
permitted by Delaware Law, the personal liability of a director to the Company
or its stockholders for monetary damages for breach of fiduciary duty as a
director. The Company's Bylaws provide that the Company shall indemnify its
officers and directors to the fullest extent permitted by Delaware Law against
all expense, liability and loss, including attorneys' fees, actually and
reasonably incurred and may purchase and maintain insurance against any
liability asserted and incurred by reason of serving as such, whether or not the
Company has the power to indemnify against such liability. The Company has
entered into indemnification agreements with its officers and directors
containing provisions which are in some respects broader than the specific
indemnification provisions contained in Delaware Law and which require that, to
the extent the Company maintains liability insurance applicable to officers or
directors, each officer and director shall be covered by such policies to the
same extent as are accorded the most favorably insured of the Company's officers
or directors, as the case may be.

     Insofar as indemnification for liabilities arising under the Securities Act
may be permitted to directors, officers, or persons controlling the Company
pursuant to the foregoing provisions and agreements, the Company has been
informed that in the opinion of the Securities and Exchange Commission, such
indemnification is against public policy as expressed in the Securities Act and
is therefore unenforceable.

ITEM 7.    EXEMPTION FROM REGISTRATION CLAIMED.

     This Item is not applicable.

ITEM 8.    EXHIBITS.

Exhibit No.                         Description
-----------                         -----------

  4.1             Amended and Restated Certificate of Incorporation of the
                  Company (filed as Exhibit A to the Company's Registration
                  Statement on Form 8-A (File No. 1-14443) as filed on July 7,
                  1999 and incorporated herein by reference).

  4.2(a)          Bylaws of the Company (filed as Exhibit B(1) to the Company's
                  Registration Statement on Form 8-A (File No. 1-14443) as filed
                  on July 7, 1999 and incorporated herein by reference).

  4.2(b)          Amendment to Bylaws of the Company (filed as Exhibit B(2) to
                  the Company's Registration Statement on Form 8-A (File No.
                  1-14443) as filed on July 7, 1999 and incorporated herein by
                  reference).

  4.3             Form of Certificate for Common Stock, Class A (filed as
                  Exhibit 4.2 to the

                                      II-2
6
                  Company's Registration Statement on Form S-1 (File No.
                  33-67576) and incorporated herein by reference).

      5.1*        Opinion of Shipman & Goodwin LLP as to the legality of the
                  securities being registered.

     23.1*        Consent of Shipman & Goodwin LLP (included in Exhibit 5.1).

     23.2*        Consent of KPMG LLP.

     24.1*        Power of Attorney (included in the signature page of this
                  registration statement).

     99.1*        Gartner Group, Inc. 1999 Stock Option Plan.

*Filed herewith.

ITEM 9.    UNDERTAKINGS.

     (a)   The undersigned registrant hereby undertakes:

           (1) To file, during any period in which offers or sales are being
made, a post-effective amendment to this registration statement to include any
material information with respect to the plan of distribution not previously
disclosed in the registration statement or any material change to such
information in the registration statement.

           (2) That, for the purpose of determining any liability under the
Securities Act, each such post-effective amendment shall be deemed to be a new
registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

           (3) To remove from registration by means of a post-effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

     (b)   The undersigned registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act, each filing of the
registrant's annual report pursuant to Section 13 or Section 15(d) of the
Exchange Act (and, where applicable, each filing of an employee benefit plan's
annual report pursuant to Section 15(d) of the Exchange Act) that is
incorporated by reference in the registration statement shall be deemed to be a
new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

     (c)   Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling persons
of the registrant pursuant to the foregoing provisions, or otherwise, the
registrant has been advised that in the opinion of the Securities and Exchange
Commission such indemnification is against public policy as expressed in the
Securities Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
registrant of expenses incurred or paid by a director, officer or controlling
person of the registrant in the successful defense of any action, suit

                                      II-3
7
or proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Securities
Act and will be governed by the final adjudication of such issue.

                                      II-4
8
                                   SIGNATURES

     Pursuant to requirements of the Securities Act of 1933, the registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this registration
statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Stamford, State of Connecticut on February 15, 2000.

                                  GARTNER GROUP, INC.

                                  By: /s/ MICHAEL D. FLEISHER
                                      -------------------------------------
                                      Michael D. Fleisher
                                      President and Chief Executive Officer

                                POWER OF ATTORNEY

     Know All Persons by These Presents, that each person whose signature
appears below constitutes and appoints Michael D. Fleisher and Regina M.
Paolillo and each of them acting individually, as his or her true and lawful
attorneys-in-fact and agents, with full power of substitution and resubstitution
for him or her and in his or her name, place and stead, in any and all
capacities to sign any and all amendments (including post-effective amendments)
to this registration statement, and to file same, with all exhibits thereto, and
other documents in connection therewith with the Securities and Exchange
Commission, with full power and authority to do and perform each and every act
and thing requisite or necessary to be done in and about the premises, as fully
to all intents and purposes as he or she might or could do in person, hereby
ratifying and confirming all that said attorneys-in-fact and agents or any of
them, of their or his substitute or substitutes, may lawfully do or cause to be
done by virtue hereof.

     Pursuant to the requirements of the Securities Act of 1933, this
registration statement has been signed by the following persons in the
capacities and on the dates indicated.
SIGNATURE                                 TITLE                               DATE
          ---------                                 -----                               ----
/s/ MANUEL A . FERNANDEZ               Director, Chairman of the Board            February 15, 2000
--------------------------------
  Manuel A. Fernandez

/s/MICHAEL D. FLEISHER                 Director, President and Chief              February 15, 2000
--------------------------------       Executive Officer (Principal
  Michael D. Fleisher                  Executive Officer)

/s/ REGINA M. PAOLILLO                 Executive Vice President Finance and       February 15, 2000
--------------------------------       Administration and Chief Financial
  Regina M. Paolillo                   Officer
                                       (Principal Financial and Accounting
                                       Officer)

/s/ANNE SUTHERLAND FUCHS               Director                                   February 15, 2000
--------------------------------
  Anne Sutherland Fuchs

    /s/ WILLIAM O. GRABE               Director                                   February 15, 2000
--------------------------------
  William O. Grabe
II-5
9
/s/ MAX D. HOPPER                Director                                   February 15, 2000
--------------------------------
  Max D. Hopper

   /s/ JOHN P. IMLAY, JR.              Director                                   February 15, 2000
--------------------------------
  John P. Imlay, Jr.

   /s/ CHARLES B. MCQUADE              Director                                   February 15, 2000
--------------------------------
  Charles B. McQuade

   /s/ STEPHEN G. PAGLIUCA             Director                                   February 15, 2000
--------------------------------
  Stephen G. Pagliuca

      /s/ KENNETH ROMAN                Director                                   February 15, 2000
--------------------------------
  Kenneth Roman

     /s/ DENNIS G. SISCO               Director                                   February 15, 2000
--------------------------------
  Dennis G. Sisco
II-6
10
                                  EXHIBIT INDEX

Exhibit No.                                 Description
-----------                                 -----------

    4.1          Amended and Restated Certificate of Incorporation of the
                 Company (filed as Exhibit A to the Company's Registration
                 Statement on Form 8-A (File No. 1-14443) as filed on July 7,
                 1999 and incorporated herein by reference).

    4.2(a)       Bylaws of the Company (filed as Exhibit B(1) to the
                 Company's Registration Statement on Form 8-A (File No.
                 1-14443) as filed on July 7, 1999 and incorporated herein by
                 reference).

    4.2(b)       Amendment to Bylaws of the Company (filed as Exhibit B(2) to
                 the Company's Registration Statement on Form 8-A (File No.
                 1-14443) as filed on July 7, 1999 and incorporated herein by
                 reference).

    4.3          Form of Certificate for Common Stock, Class A (filed as Exhibit
                 4.2 to the Company's Registration Statement on Form S-1 (File
                 No. 33-67576) and incorporated herein by reference).

    5.1*         Opinion of Shipman & Goodwin LLP as to the legality of the
                 securities being registered.

   23.1*         Consent of Shipman & Goodwin LLP (included in Exhibit 5.1).

   23.2*         Consent of KPMG LLP.

   24.1*         Power of Attorney (included in the signature page of this
                 registration statement).

   99.1*         Gartner Group, Inc. 1999 Stock Option Plan.

*Filed herewith.