As filed with the Securities and Exchange Commission on October 8, 1998
                                                      Registration No. 333-56589

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549
                                    --------

                        POST-EFFECTIVE AMENDMENT NO. 1 ON
                                    FORM S-8
                       TO FORM S-4 REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933*
                                    --------

                                 CITIGROUP INC.
             (Exact name of registrant as specified in its charter)

          Delaware                                    52-1568099
(State or other jurisdiction                       (I.R.S. employer 
of incorporation or organization)                 identification no.)
                                    --------

           399 Park Avenue                               10043
            New York, NY                               (Zip Code)
(Address of principal executive offices)


                       Citicorp 1988 Stock Incentive Plan
                       Citicorp 1997 Stock Incentive Plan
                        Citicorp 1994 Stock Purchase Plan
                 Citicorp Executive Incentive Compensation Plan
                         Citibank Savings Incentive Plan
                            (Full title of the plan)
    

                               Stephanie B. Mudick
                         General Counsel - Corporate Law
                                 Citigroup Inc.
                              153 East 53rd Street
                               New York, NY 10043
                    (Name and address of agent for service)

                                 (212) 559-1000
                       (Telephone number, including area
                          code, for agent for service)


                                    ---------

<TABLE>

                         CALCULATION OF REGISTRATION FEE

<CAPTION>

Title of securities to       Amount to be         Proposed maximum        Proposed maximum           Amount of
     be registered            registered         offering price per      aggregate offering      registration fee
                                                        share                   price
------------------------ ---------------------- ---------------------- ------------------------ --------------------
<S>                          <C>                      <C>              <C>                            <C>

Common Stock, $.01 par
value per share              45,754,813(1)            $61.25(2)        $2,802,482,296                 $ 0 (2)

------------------------ ---------------------- ---------------------- ------------------------ --------------------
<FN>

(1)   The number of shares to be  registered  is based upon an  estimate  of the
      maximum  number of shares of common stock,  par value $1.00 per share,  of
      Citicorp ("Citicorp Common Stock") that were outstanding or issuable under
      the Plans (as herein  defined)  or  otherwise  expected to be issued on or
      before the Effective  Time of the Merger (as described in the  Explanatory
      Note)  multiplied by the exchange ratio of 2.5 shares of common stock, par
      value $.01 per share of the Registrant.

(2)   The  proposed  maximum  offering  price  was  calculated  and  the fee was
      previously paid in connection with the Registrant's Registration Statement
      on Form S-4 (No. 333-56589), declared effective on June 11, 1998.
</FN>
</TABLE>

*Filed as a Post-Effective  Amendment on Form S-8 to such Registration Statement
pursuant to the procedure described herein - see "Explanatory Note".


<PAGE>


                                EXPLANATORY NOTE


      Citigroup  Inc.  ("Citigroup")  (formerly  Travelers  Group Inc.),  hereby
amends  its  Registration  Statement  on  Form  S-4  (No.  333-56589),  declared
effective on June 11, 1998 (the "S-4"), by filing this Post-Effective  Amendment
No. 1 on Form S-8 relating to up to 45,754,813  shares of common stock, $.01 par
value per share, of Citigroup  ("Citigroup Common Stock"),  issuable pursuant to
the  provisions  of the  Citicorp  1988 Stock  Incentive  Plan (the "1988  Stock
Incentive  Plan"),  the  Citicorp  1997 Stock  Incentive  Plan (the "1997  Stock
Incentive  Plan"),  the Citicorp 1994 Stock  Purchase Plan (the "Stock  Purchase
Plan") and the Citicorp  Executive  Incentive  Compensation Plan (the "Executive
Incentive  Compensation  Plan"),  all of which have been  assumed  by  Citigroup
pursuant to the Merger  Agreement  defined and described below, and the Citibank
Savings  Incentive  Plan  (the  "Savings  Incentive  Plan")   (collectively  the
"Plans").

      Pursuant to the  Agreement  and Plan of Merger  dated as of April 5, 1998,
between Citicorp and Travelers Group Inc. ("Travelers"), as amended by a certain
letter  agreement dated June 8, 1998 among  Citicorp,  Travelers and Citi Merger
Sub Inc. ("Citi Merger Sub"), and the  transactions  contemplated  thereby,  (i)
Citicorp merged with and into Citi Merger Sub (the  "Merger"),  with Citi Merger
Sub continuing as the surviving  corporation  and changing its name to Citicorp;
(ii)  Travelers  changed its name to Citigroup  Inc.  (iii) each share of common
stock,  par value  $1.00 per share of Citicorp  (the  "Citicorp  Common  Stock")
issued and  outstanding  immediately  prior to the Effective  Time of the Merger
(the  "Effective  Time") was  converted  into the right to receive 2.5 shares of
Citigroup  Common Stock; and (iv) at the Effective Time,  Citigroup  assumed all
outstanding obligations to issue Citicorp Common Stock under the Plans.

      This  Post-Effective  Amendment  relates to an  aggregate  amount of up to
45,754,813  shares of Citigroup Common Stock issuable pursuant to the Plans (the
"Plan  Shares").  When the S-4 was  filed,  Citigroup  registered  1,174,986,185
shares of  Citigroup  Common  Stock,  which  included  the Plan Shares that were
reserved  and were  expected  to be issued  under  the  Plans on or  before  the
Effective Time of the Merger.

      The designation of this Post-Effective Amendment No. 1 as Registration No.
333-56589  denotes that this  Post-Effective  Amendment relates only to the Plan
Shares and that this is the first Post-Effective Amendment to the S-4 filed with
respect to the Plan Shares.


<PAGE>


                                     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 Annual  Report on Form 10-K  filed by  Travelers  Group Inc.  (the
former  name of  Citigroup  Inc.) (the  "Registrant")  for the fiscal year ended
December 31, 1997, as amended.

      (b) All other  reports  filed by  Registrant  pursuant to Section 13(a) or
15(d) of the Securities Exchange Act of 1934 (the "Exchange Act"), since the end
of the fiscal year covered by the annual report referred to in (a) above.

      (c) The  description  of the  Registrant's  Common Stock  contained in the
Registrant's  registration statement filed under the Exchange Act, as updated by
the  description  of the  Registrant's  Common Stock  contained in the Company's
Registration Statement on Form S-4 dated June 11, 1998 (File No. 333-56589), and
any  amendment  or  report  filed  for the  purpose  of  further  updating  such
description.

      All documents  subsequently  filed by the  Registrant  pursuant to Section
13(a),  13(c),  14 and  15(d) of the  Exchange  Act,  prior to the  filing  of a
post-effective amendment which indicates that all securities offered hereby have
been sold or which  deregisters all securities then remaining  unsold,  shall be
deemed to be incorporated  by reference  herein and to be a part hereof from the
date of the filing of such documents.

Item 4.  Description of Securities.

         Not applicable.

Item 5.  Interests of Named Experts and Counsel.

         Not applicable.

Item 6.  Indemnification of Directors and Officers.

      Subsection  (a) of Section 145 of the  Delaware  General  Corporation  Law
("DGCL") empowers a corporation to indemnify any person who was or is a party or
threatened to be made a party to any  threatened,  pending or completed  action,
suit or proceeding,  whether civil,  criminal,  administrative  or investigative
(other  than an action by or in the right of the  corporation)  by reason of the
fact that the person is or was a  director,  officer,  employee  or agent of the
corporation  or is or  was  serving  at the  request  of  the  corporation  as a
director, officer, employee or agent of another corporation,  partnership, joint
venture,  trust or other  enterprise,  against  expenses  (including  attorneys'
fees),  judgments,  fines and amounts paid in settlement actually and reasonably
incurred by the person in connection with such action, suit or proceeding if the
person acted in good faith and in a manner the person reasonably  believed to be
in or not opposed to the best interests of the


<PAGE>

corporation,  and,  with respect to any criminal  action or  proceeding,  had no
reasonable cause to believe the person's conduct was unlawful.

      Subsection (b) of DGCL Section 145 empowers a corporation to indemnify any
person  who  was or is a  party  or is  threatened  to be  made a  party  to any
threatened,  pending  or  completed  action  or suit by or in the  right  of the
corporation  to procure a judgment  in its favor by reason of the fact that such
person  acted  in  any of the  capacities  set  forth  above,  against  expenses
(including  attorneys'  fees) actually and reasonably  incurred by the person in
connection  with the defense or  settlement of such action or suit if the person
acted in good  faith  and in a manner  he  reasonably  believed  to be in or not
opposed to the best interest of the corporation,  except that no indemnification
may be made in  respect of any  claim,  issue or matter as to which such  person
shall have been adjudged to be liable to the corporation  unless and only to the
extent  that the Court of Chancery or the court in which such action or suit was
brought shall  determine upon  application  that,  despite the  adjudication  of
liability  but in view of all the  circumstances  of the  case,  such  person is
fairly and reasonably entitled to indemnity for such expenses which the Court of
Chancery or such other court shall deem proper.

      Other  subsections  of Section  145 further  provide  that to the extent a
present or former  director or officer of a corporation  has been  successful on
the  merits or  otherwise  in the  defense  of any  action,  suit or  proceeding
referred to in subsections  (a) and (b) of Section 145, or in the defense of any
claim,  issue or  matter  therein,  such  person  shall be  indemnified  against
expenses  (including  attorneys' fees) actually and reasonably  incurred by such
person in connection therewith; that indemnification provided for by Section 145
shall not be deemed exclusive of any other rights to which the indemnified party
may be entitled; that indemnification  provided for by Section 145 shall, unless
otherwise provided when authorized or ratified,  continue as to a person who has
ceased to be a  director,  officer,  employee  or agent  and shall  inure to the
benefit of such person's heirs,  executors and administrators;  and empowers the
corporation  to  purchase  and  maintain  insurance  on behalf of a director  or
officer of the corporation  against any liability  asserted  against such person
and  incurred  by such  person  in any such  capacity,  or  arising  out of such
person's status as such,  whether or not the corporation would have the power to
indemnify such person against such  liabilities  under Section 145. Section 4 of
Article IV of the Registrant's By-Laws provides that the Company shall indemnify
its directors and officers to the fullest extent permitted by the DGCL.

      The  Registrant  also provides  liability  insurance for its directors and
officers  which  provides  for  coverage  against  loss from claims made against
directors and officers in their capacity as such,  including  liabilities  under
the Securities Act of 1933, as amended.  In certain employment  agreements,  the
Registrant or its  subsidiaries  have also agreed to indemnify  certain officers
against  loss from claims made  against  such  officers in  connection  with the
performance   of  their  duties   under  their   employment   agreements.   Such
indemnification  is generally to the same extent as provided in the Registrant's
By-Laws.

      Section 102(b)(7) of the DGCL provides that a certificate of incorporation
may contain a provision  eliminating  or limiting  the  personal  liability of a
director to the corporation or its  stockholders for monetary damages for breach
of fiduciary duty as a director provided that such provision shall not eliminate
or limit the liability of a director (i) for any breach of the  director's  duty
of loyalty to the  corporation or its  stockholders,  (ii) for acts or omissions
not in good faith or which involve intentional misconduct or a knowing violation
of law,  (iii) under Section 174 of the DGCL, or (iv) for any  transaction  from
which the director derived an improper  personal  benefit.  Article TENTH of the
Registrant's  Restated  Certificate  of  Incorporation  limits the  liability of
directors to the fullest extent permitted by Section 102(b)(7).

Item 7.  Exemption from Registration Claimed.

         Not applicable.


<PAGE>


Item 8.  Exhibits.

         See Exhibit Index attached hereto.

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:

            (i) To include any  prospectus  required by Section  10(a)(3) of the
      Securities Act of 1933;

            (ii) To reflect in the  prospectus any facts or events arising after
      the  effective  date of the  registration  statement  (or the most  recent
      post-effective amendment thereof) which, individually or in the aggregate,
      represent  a  fundamental  change  in the  information  set  forth  in the
      registration  statement.  Notwithstanding  the foregoing,  any increase or
      decrease in volume of  securities  offered (if the total  dollar  value of
      securities  offered  would not exceed that which was  registered)  and any
      deviation from the low or high end of the estimated maximum offering range
      may be  reflected  in the form of  prospectus  filed  with the  Commission
      pursuant  to Rule 424(b) if, in the  aggregate,  the changes in volume and
      price  represent no more than 20 percent  change in the maximum  aggregate
      offering price set forth in the "Calculation of Registration Fee" table in
      the effective registration statement;

            (iii) 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;
      provided,  however,  that paragraphs (a)(1)(i) and (a)(1)(ii) do not apply
      if the  registration  statement is on Form S-3,  Form S-8 or Form F-3, and
      the information  required to be included in a post-effective  amendment by
      those  paragraphs is contained in periodic reports filed with or furnished
      to the  Securities and Exchange  Commission by the registrant  pursuant to
      Section 13 or Section  15(d) of the  Securities  Exchange Act of 1934 that
      are incorporated by reference in the registration statement.

      (2)  That,  for  the  purpose  of  determining  any  liability  under  the
Securities Act of 1933, 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; and

      (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 of 1933, each filing of the
registrant's  annual report pursuant to Section 13(a) or 15(d) of the Securities
Exchange Act of 1934 (and, where applicable,  each filing of an employee benefit
plan's annual report pursuant to Section 15(d) of the Securities Exchange Act of
1934) 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.


<PAGE>

      (c)  Insofar  as  indemnification   for  liabilities   arising  under  the
Securities Act of 1933 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 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 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 Act and will
be governed by the final adjudication of such issue.


<PAGE>

                                   SIGNATURES

      Pursuant to the  requirements  of the  Securities Act of 1933, as amended,
Citigroup Inc. certifies that it has reasonable grounds to believe that it meets
all of the requirements for filing this Post-Effective  Amendment on Form S-8 to
the Registration  Statement (No. 333-56589) on Form S-4 (the "Form S-4") and has
duly  caused  this  Registration  Statement  to be signed  on its  behalf by the
undersigned,  thereunto duly  authorized,  in The City of New York, State of New
York, this 8th day of October 1998.



                                              Citigroup Inc.
                                              (Registrant)

                                              By /s/ James Dimon
                                                 ---------------
                                                 James Dimon,
                                                 President

      Pursuant to the  requirements  of the  Securities Act of 1933, as amended,
this Post-Effective  Amendment on Form S-8 to the Form S-4 has been signed below
by the following persons in the capacities indicated on this 8th day of October,
1998.


             Signature                                  Capacity
             ---------                                  --------

                                            Chairman of the Board, Co-Chief
         /s/ John S. Reed                   Executive Officer (Principal
         ----------------------             Executive Officer) and Director
         John S. Reed
                                            Chairman of the Board, Co-Chief
         /s/ Sanford I. Weill               Executive Officer (Principal
         ----------------------             Executive Officer) and Director
         Sanford I. Weill

                                            Executive Vice President and
         /s/ Heidi G. Miller                Chief Financial Officer
         ----------------------             (Principal Financial Officer)
         Heidi G. Miller

                                            Executive Vice President and Chief
         /s/ Irwin R. Ettinger              Accounting Officer (Principal
         ----------------------             Accounting Officer)
         Irwin R. Ettinger


                  
         ----------------------             Director
         C. Michael Armstrong


<PAGE>


                  *
         ----------------------             Director
         Judith Arron


                  *
         ----------------------             Director
         Alain J. P. Belda


                  *
         ----------------------             Director
         Kenneth J. Bialkin


                  *
         ----------------------             Director
         Kenneth T. Derr


                  *
         ----------------------             Director
         John M. Deutch


                  *
         ----------------------             Director
         Ann Dibble Jordan


                  *
         ----------------------             Director
         Reuben Mark


                  *
         ----------------------             Director
         Michael T. Masin


                  *
         ----------------------             Director
         Dudley C. Mecum


                  *
         ----------------------             Director
         Richard D. Parsons


                  *
         ----------------------             Director
         Andrall E. Pearson


<PAGE>




                  *
         ----------------------             Director
         Robert B. Shapiro


                  *
         ----------------------             Director
         Franklin A. Thomas


                  *
         ----------------------             Director
         Edgar S. Woolard


                  *
         ----------------------             Director
         Arthur Zankel



*By:   /s/ James Dimon
       -------------------------
       James Dimon, as
       Attorney-in-fact under the
       Powers of Attorney filed
       as Exhibit 24 hereto.


<PAGE>


                                 EXHIBIT INDEX

Exhibit
Number            Description of Document

5                 Opinion of Stephanie B. Mudick,
                  with respect to the legality of the securities
                  being registered

23.1              Consent of Stephanie B. Mudick
                  (included in the opinion filed as Exhibit 5)

23.2              Consent of KPMG Peat Marwick LLP

23.3              Consent of KPMG Peat Marwick LLP

23.4              Consent of Arthur Andersen LLP

24                Powers of Attorney of certain directors of the Registrant.