FORM 10-Q

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                   Quarterly Report Under Section 13 or 15(d)
                     of the Securities Exchange Act of 1934

For Quarter Ended:  September 30, 1998

Commission file number:  1-10551

                               Omnicom Group Inc.
             (Exact name of registrant as specified in its charter)

            New York                                       13-1514814
(State or other jurisdiction of                          (IRS Employer
 incorporation or organization)                        Identification No.)

 437 Madison Avenue, New York, New York                       10022
(Address of principal executive offices)                    (Zip Code)

          (212) 415-3600
(Registrant's telephone number, including area code)

Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days. Yes _X_ No ___

The number of shares of common stock of the Company issued and outstanding at
October 31, 1998 is 168,695,900.



                       OMNICOM GROUP INC. AND SUBSIDIARIES
                                      INDEX

                                                                        Page No.
                                                                        --------
PART I. FINANCIAL INFORMATION

      Item 1. Financial Statements:

               Consolidated Condensed Balance Sheets -
                  September 30, 1998, December 31, 1997 and
                  September 30, 1997                                       2

               Consolidated Condensed Statements of Income -
                  Three Months and Nine Months
                  Ended September 30, 1998 and 1997                        3

               Consolidated Condensed Statements of Cash Flows -
                  Nine Months Ended September 30, 1998 and 1997            4

               Notes to Consolidated Condensed Financial
                  Statements                                               5-11

      Item 2. Management's Discussion of Financial Condition
                 and Results of Operations                                12-21

PART II. OTHER INFORMATION

      Item 6. Exhibits                                                    22


                                      -1-


                          PART I. FINANCIAL INFORMATION
                          Item 1. Financial Statements
                       OMNICOM GROUP INC. AND SUBSIDIARIES
                     CONSOLIDATED CONDENSED BALANCE SHEETS
                             (Dollars in Thousands)



                            Assets                   September 30,   December 31, September 30,
                            ------                       1998            1997         1997
                                                      ----------     -----------   ----------
                                                                                         
Current assets:
     Cash and cash equivalents                        $  313,234     $  556,436    $  238,253
     Investments available-for-sale, at                                            
        market, which approximates cost                   34,271         87,668        71,644
     Accounts receivable, less allowance                                           
        for doubtful accounts of                                                   
        $43,333, $32,190 and $27,139                   2,286,340      1,908,532     1,691,987
     Billable production orders in process               287,412        183,145       217,275 
     Prepaid expenses and other current assets           428,201        252,617       253,434
                                                      ----------     ----------    ----------
         Total current assets                          3,349,458      2,988,398     2,472,593
Furniture, equipment and leasehold improvements                                    
  at cost, less accumulated depreciation and                                       
  amortization of $388,967, $336,926 and $329,403        301,528        239,667       228,789
Investments in affiliates                                324,422        281,264       277,662
Intangibles, less amortization of $277,484,                                        
  $235,257 and $215,369                                1,927,443      1,234,539     1,161,287
Deferred tax benefits                                     90,941         68,086        75,693
Deferred charges and other assets                        230,545        153,789       172,055
                                                      ----------     ----------    ----------
         Total assets                                 $6,224,337     $4,965,743    $4,388,079
                                                      ==========     ==========    ==========
          Liabilities and Shareholders' Equity                                        
          ------------------------------------                                        
                                                                                   
Current liabilities:                                                               
     Accounts payable                                 $2,404,932     $2,595,255    $1,838,341
     Payable to banks and current portion of                                       
        long term debt                                   123,154         17,672       104,881
     Other accrued liabilities                         1,186,694        885,569       750,439
     Accrued taxes on income                              51,005         80,489        78,331
                                                      ----------     ----------    ----------
         Total current liabilities                     3,765,785      3,578,985     2,771,992
Long term debt                                           619,603        123,165       378,003
Convertible subordinated debentures                      448,500        218,500       218,500
Deferred compensation and other liabilities              245,780        114,668       140,205
Minority interests                                        77,292         63,686        59,583
                                                                                   
Shareholders' equity:                                                              
     Common stock                                         88,656         86,918        86,832
     Additional paid-in capital                          643,682        533,412       526,743
     Retained earnings                                   680,782        555,038       500,435
     Unamortized restricted stock                        (64,873)       (46,745)      (51,368)
     Cumulative translation adjustment                   (55,366)       (47,947)      (46,145)
     Treasury stock                                     (225,504)      (213,937)     (196,701)
                                                      ----------     ----------    ----------
         Total shareholders' equity                    1,067,377        866,739       819,796
                                                      ----------     ----------    ----------
         Total liabilities and shareholders' equity   $6,224,337     $4,965,743    $4,388,079
                                                      ==========     ==========    ==========

 
The accompanying  notes to consolidated  condensed  financial  statements are an
integral part of these balance sheets.


                                      -2-


                       OMNICOM GROUP INC. AND SUBSIDIARIES
                   CONSOLIDATED CONDENSED STATEMENTS OF INCOME
                  (Dollars in Thousands, Except Per Share Data)



                                          Three Months Ended September 30,   Nine Months Ended September 30,
                                          --------------------------------   -------------------------------
                                               1998           1997              1998              1997
                                               ----           ----              ----              ----
                                                                                          
Revenues:
   Commissions and fees                      $981,577       $746,839          $2,894,063       $2,229,757

Operating expenses:
   Salaries and related costs                 587,246        452,927           1,708,881        1,318,612
   Office and general expenses                283,311        214,028             800,176          634,397
                                             --------       --------          ----------       ----------
            Total operating expenses          870,557        666,955           2,509,057        1,953,009
                                             --------       --------          ----------       ----------
Operating profit                              111,020         79,884             385,006          276,748

Net interest expense:
   Interest and dividend income                (6,429)        (5,532)            (20,547)         (14,789)
   Interest paid or accrued                    17,935         12,356              50,151           30,923
                                             --------       --------          ----------       ----------
            Net interest expense               11,506          6,824              29,604           16,134
                                             --------       --------          ----------       ----------
Income before income taxes                     99,514         73,060             355,402          260,614

Income taxes:
   Federal                                     14,610         10,557              58,940           39,497
   State and local                              4,911          4,935              17,353           15,397
   International                               22,685         14,387              73,676           51,296
                                             --------       --------          ----------       ----------
            Total income taxes                 42,206         29,879             149,969          106,190
                                             --------       --------          ----------       ----------
Income after income taxes                      57,308         43,181             205,433          154,424
Equity in affiliates                            5,948          4,601              16,206           16,027
Minority interests                             (9,464)        (6,291)            (30,952)         (22,493)
                                             --------       --------          ----------       ----------
            Net income                       $ 53,792       $ 41,491          $  190,687       $  147,958
                                             ========       ========          ==========       ==========
Earnings per share:
   Net income:
           Basic                             $   0.32       $   0.26          $     1.15       $     0.93
           Diluted                           $   0.32       $   0.26          $     1.13       $     0.91

Dividends declared per common share          $  0.125       $  0.125          $    0.375       $    0.325



The accompanying  notes to consolidated  condensed  financial  statements are an
integral part of these statements.


                                      -3-


                       OMNICOM GROUP INC. AND SUBSIDIARIES
                 CONSOLIDATED CONDENSED STATEMENTS OF CASH FLOWS
                             (Dollars in Thousands)

                                                            Nine Months Ended
                                                              September 30,
                                                          ---------------------
                                                             1998       1997
                                                          ---------   ---------
Cash flows from operating activities:
     Net income                                           $ 190,687   $ 147,958
     Adjustments to reconcile net income to net cash
       used for operating activities:
     Depreciation and amortization of tangible assets        55,531      42,895
     Amortization of intangible assets                       39,415      29,421
     Minority interests                                      30,952      22,493
     Earnings of affiliates in excess of 
       dividends received                                    (5,874)     (9,641)
     Decrease in deferred tax benefits                        3,704       2,165
     Provision for losses on accounts receivable              6,135       5,030
     Amortization of restricted shares                       15,446      12,924
     Increase in accounts receivable                        (30,754)   (143,256)
     Increase in billable production                        (80,990)    (62,714)
     Increase in other current assets                       (72,912)    (43,209)
     Decrease in accounts payable                          (470,376)   (210,770)
     Decrease in other accrued liabilities                  (28,242)     (4,019)
     (Decrease) increase in accrued income taxes            (36,967)      9,606
     Other                                                  (29,935)    (37,563)
                                                          ---------   ---------
         Net cash used for operating activities            (414,180)   (238,680)
                                                          ---------   ---------

Cash flows from investing activities:
     Capital expenditures                                   (65,270)    (47,251)
     Payments for purchases of equity interests in
       subsidiaries and affiliates, net of cash acquired   (460,623)   (300,622)
     Proceeds from sales of equity interests in
       subsidiaries and affiliates                            4,147         466
     Payments for purchases of investments 
       available-for-sale and other investments             (38,930)    (88,526)
     Proceeds from sales of investments 
       available-for-sale and other investments              92,776      34,056
                                                          ---------   ---------
         Net cash used for investing activities            (467,900)   (401,877)
                                                          ---------   ---------

Cash flows from financing activities:
     Net borrowings under lines of credit                     8,090      76,784
     Share transactions under employee stock plans           46,815      26,247
     Proceeds from issuance of shares                       171,084        --
     Proceeds from issuance of principal of debt 
         obligations                                        751,368     471,997
     Repayment of principal of debt obligations            (111,924)    (41,722)
     Dividends and loans to minority stockholders           (28,254)    (27,934)
     Dividends paid                                         (61,619)    (47,704)
     Purchase of treasury shares                           (128,334)    (52,223)
                                                          ---------   ---------
         Net cash provided by financing activities          647,226     405,445
                                                          ---------   ---------

Effect of exchange rate changes on cash and 
     cash equivalents                                        (8,348)    (36,902)
                                                          ---------   ---------
     Net decrease in cash and cash equivalents             (243,202)   (272,014)
Cash and cash equivalents at beginning of period            556,436     510,267
                                                          ---------   ---------
Cash and cash equivalents at end of period                $ 313,234   $ 238,253
                                                          =========   =========

Supplemental Disclosures:
     Income taxes paid                                    $ 151,702   $  96,750
                                                          =========   =========
     Interest paid                                        $  44,309   $  27,049
                                                          =========   =========

The accompanying  notes to consolidated  condensed  financial  statements are an
integral part of these statements.


                                      -4-


                       OMNICOM GROUP INC. AND SUBSIDIARIES
              NOTES TO CONSOLIDATED CONDENSED FINANCIAL STATEMENTS

===============================================================================

1)        The  consolidated  condensed  interim  financial  statements  included
     herein have been prepared by the Company,  without  audit,  pursuant to the
     rules and  regulations of the Securities and Exchange  Commission.  Certain
     information  and  footnote   disclosures  normally  included  in  financial
     statements  prepared  in  accordance  with  generally  accepted  accounting
     principles  have been  condensed  or  omitted  pursuant  to such  rules and
     regulations.

2)        These  statements  reflect  all  adjustments,   consisting  of  normal
     recurring accruals which, in the opinion of management, are necessary for a
     fair   presentation  of  the   information   contained   therein.   Certain
     reclassifications have been made to the September 30, 1997 reported amounts
     to  conform  them  with the  September  30,  1998  and  December  31,  1997
     presentation.  Also,  all amounts  presented  give effect to a  two-for-one
     stock  split in the form of a 100% stock  dividend  completed  in  December
     1997. These consolidated  condensed financial  statements should be read in
     conjunction  with the consolidated  financial  statements and notes thereto
     included  in the  Company's  annual  report on Form 10-K for the year ended
     December 31, 1997.

3)        Results  of  operations  for  interim   periods  are  not  necessarily
     indicative of annual results.


                                      -5-


                       OMNICOM GROUP INC. AND SUBSIDIARIES
         NOTES TO CONSOLIDATED CONDENSED FINANCIAL STATEMENTS(CONTINUED)

================================================================================

4)        Basic earnings per share is based upon the weighted  average number of
     common shares outstanding during the period.  Diluted earnings per share is
     based on such average  number of common  shares  outstanding,  common share
     equivalents  outstanding,  and if  dilutive,  is  adjusted  for the assumed
     conversion of the Company's  convertible  subordinated  debentures  and the
     assumed  increase  in net  income for the after tax  interest  cost of such
     debentures.  At September  30,  1998,  the 2.25%  Convertible  Subordinated
     Debentures  had been  outstanding  since  January  6,  1998  and the  4.25%
     Convertible  Subordinated  Debentures had been  outstanding  for the entire
     nine months.  At September  30, 1997,  the 4.25%  Convertible  Subordinated
     Debentures had been outstanding since January 3, 1997. The number of shares
     used in the  computations  of basic and diluted  earnings per share were as
     follows:

                             Three Months                   Nine Months
                          Ended September 30,           Ended September 30,
                          -------------------           -------------------
                         1998            1997           1998           1997
                         ----            ----           ----           ----
   Basic EPS          166,599,500    159,657,500     165,604,400     159,575,600
   Diluted EPS        169,915,300    162,869,500     175,845,400     162,572,500

          For  purposes of  computing  diluted  earnings per share for the three
     months ended September 30, 1998,  neither the Company's  2.25%  Convertible
     Subordinated  Debentures nor the Company's 4.25%  Convertible  Subordinated
     Debentures were reflected in the computation, as their inclusion would have
     been anti-dilutive. For the purposes of computing diluted


                                      -6-


                       OMNICOM GROUP INC. AND SUBSIDIARIES
         NOTES TO CONSOLIDATED CONDENSED FINANCIAL STATEMENTS(CONTINUED)

================================================================================

     earnings per share for the nine months ended  September 30, 1998, the 2.25%
     Convertible  Subordinated Debentures were not reflected in the computation,
     as their inclusion would have been anti-dilutive.

          For purposes of computing diluted earnings per share for the three and
     nine months ended  September 30, 1997, the 4.25%  Convertible  Subordinated
     Debentures were not reflected in the computation,  as their inclusion would
     have been anti-dilutive.

5)        The Company  has adopted the  provisions  of  Statement  of  Financial
     Accounting  Standards  No. 130,  "Reporting  Comprehensive  Income",  which
     requires  presentation  of  information  on  comprehensive  income  and its
     components in financial  statements.  In the Company's case,  comprehensive
     income includes net income and foreign  currency  translation  adjustments.
     Total comprehensive income and its components were as follows:

                                   Three Months               Nine Months
                                Ended September 30,        Ended September 30,
                                -------------------        -------------------
                              (Dollars in Thousands)     (Dollars in Thousands)
                                  1998        1997           1998        1997
                                  ----        ----           ----        ----
Net Income                     $ 53,792     $ 41,491      $ 190,687   $ 147,958
Foreign Currency 
Translation Adjustments         (14,537)     (11,587)        (7,142)    (49,635)
                               --------     --------      ---------   ---------
Total Comprehensive Income     $ 39,255     $ 29,904      $ 183,545   $  98,323
                               ========     ========      =========   =========


                                      -7-


                       OMNICOM GROUP INC. AND SUBSIDIARIES
         NOTES TO CONSOLIDATED CONDENSED FINANCIAL STATEMENTS(CONTINUED)

================================================================================

6)        In  June  1998,  the  Financial   Accounting  Standards  Board  issued
     Statement  of  Financial  Accounting  Standards  No. 133 ("SFAS No.  133"),
     "Accounting for Derivative  Instruments and Hedging  Activities".  SFAS No.
     133  establishes  accounting and reporting  standards  requiring that every
     derivative instrument (including certain derivative instruments embedded in
     other  contracts)  be recorded  in the balance  sheet as either an asset or
     liability measured at its fair value. SFAS No. 133 requires that changes in
     the  derivative's  fair value be  recognized  currently in earnings  unless
     specific  hedge  accounting   criteria  are  met.  Special  accounting  for
     qualifying hedges allows a derivative's  gains and losses to offset related
     results on the hedged item in the income  statement,  and  requires  that a
     company must formally document,  designate, and assess the effectiveness of
     transactions that receive hedge accounting.

          SFAS No. 133 is effective  for fiscal years  beginning  after June 15,
     1999. A company may also  implement SFAS No. 133 as of the beginning of any
     fiscal quarter after issuance (that is, fiscal quarters  beginning June 16,
     1998 and thereafter).  SFAS No. 133 cannot be applied  retroactively.  Once
     implemented, SFAS No. 133 must be applied to (a) derivative instruments and
     (b) certain derivative instruments embedded in hybrid contracts that


                                      -8-


                       OMNICOM GROUP INC. AND SUBSIDIARIES
         NOTES TO CONSOLIDATED CONDENSED FINANCIAL STATEMENTS(CONTINUED)

================================================================================

     were issued,  acquired,  or substantively  modified after December 31, 1997
     (and, at a company's election, before January 1, 1998).

          The  Company  intends to adopt SFAS No. 133 for its fiscal year ending
     December 31, 2000. The adoption of the provisions of SFAS No. 133 would not
     have had a material  effect on the Company's  results of operations for the
     quarter  or nine  months  ending  September  30,  1998 or on its  financial
     position as of that date.

7)        In  January  1998,   the  Company   completed  the   acquisitions   of
     Fleishman-Hillard,  Inc., GPC International Holdings Inc. and Palmer Jarvis
     Inc.  These  acquisitions  have been  accounted  for under the  pooling  of
     interests method of accounting. The number of shares issued or to be issued
     by the Company in connection  with these  acquisitions  is  3,550,366.  The
     assets, liabilities,  shareholders' equity and results of operations of the
     companies  acquired  are  not,  either  individually  or in the  aggregate,
     material to the Company and, therefore,  the Company's prior year financial
     statements have not been restated.

8)        On  January  6,  1998,  the  Company  issued   $230,000,000  of  2.25%
     Convertible  Subordinated Debentures with a scheduled maturity in 2013. The
     debentures are convertible into common stock of the Company at a


                                      -9-


                       OMNICOM GROUP INC. AND SUBSIDIARIES
         NOTES TO CONSOLIDATED CONDENSED FINANCIAL STATEMENTS(CONTINUED)

================================================================================

     conversion  price of $49.83  per share  subject  to  adjustment  in certain
     events.  Debenture  holders have the right to require the Company to redeem
     the  debentures  on  January  6, 2004 at a price of  118.968%,  or upon the
     occurrence of a Fundamental Change, as defined in the indenture  agreement,
     at the prevailing  redemption price. The Company may redeem the debentures,
     as a whole or in part, on or after  December 31, 2001 initially at 112.841%
     and at increasing  prices thereafter to 118.968% until January 6, 2004, and
     100%  thereafter.  Unless the debentures are redeemed,  repaid or converted
     prior  thereto,  the  debentures  will  mature on  January 6, 2013 at their
     principal amount.  The proceeds of this issuance are being used for general
     corporate purposes, including working capital.

9)        On  January  29,  1998,  the  Company  announced  that it had  reached
     agreement  on the terms of a  recommended  cash offer for The GGT Group plc
     ("GGT"),  an advertising and marketing services group  headquartered in the
     United  Kingdom and operating  primarily in France,  the United Kingdom and
     the  United  States.  The offer  price of 200p for each share of GGT valued
     GGT's  fully  diluted   ordinary   share  capital  at  (pound)143   million
     (approximately  $235 million at the January 29, 1998  exchange  rate).  The
     acquisition  of the  entire  issued  ordinary  share  capital  of  GGT  was
     completed during the second quarter of 1998.

10)       On March 4, 1998, the Company issued  4,000,000 shares of common stock
     for aggregate proceeds before expenses of


                                      -10-


                       OMNICOM GROUP INC. AND SUBSIDIARIES
         NOTES TO CONSOLIDATED CONDENSED FINANCIAL STATEMENTS(CONTINUED)

================================================================================

     $171,400,000.  The  proceeds  of this  issuance  are being used for general
     corporate purposes, including the funding of the acquisition of GGT.

11)       On June 24,  1998,  the Company  issued  French  Francs  1,000,000,000
     (approximately  $164 million at the June 24, 1998  exchange  rate) of 5.20%
     Notes with a scheduled  maturity in 2005. The proceeds of this issuance are
     being used for general corporate purposes.


                                      -11-


             Item 2. MANAGEMENT'S DISCUSSION OF FINANCIAL CONDITION
                            AND RESULTS OF OPERATIONS

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

Results of Operations
- ---------------------
Third Quarter 1998 Compared to Third Quarter 1997
- -------------------------------------------------

      Consolidated  worldwide  revenues from commission and fee income increased
31.4% in the  third  quarter  of 1998  compared  to the third  quarter  of 1997.
Consolidated  domestic revenues  increased 26.6% in the third quarter of 1998 to
$509.2  million  compared  to  $402.3  million  in the  third  quarter  of 1997.
Consolidated international revenues increased 37.1% in the third quarter of 1998
to $472.4  million  compared  to $344.5  million  in the third  quarter of 1997.
Absent the effect of the net acquisitions of subsidiary  companies and movements
in  international  currency  exchange  rates,  consolidated  worldwide  revenues
increased  14.9% in the third  quarter of 1998  compared  to the same  period in
1997.

      Operating  expenses  increased 30.5% in the third quarter of 1998 compared
to the third  quarter  of 1997.  Excluding  the  effect  of the net  acquisition
activity and movements in international currency exchange rates mentioned above,
operating  expenses  increased  14.7% over 1997 levels.  This increase  reflects
normal salary increases and growth in client service expenditures to support the
increased revenue base.


                                      -12-


                 MANAGEMENT'S DISCUSSION OF FINANCIAL CONDITION
                      AND RESULTS OF OPERATIONS (CONTINUED)

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

      Net interest  expense  increased  by $4.7 million in the third  quarter of
1998 as compared to the same period in 1997.  This increase  primarily  reflects
higher average borrowings during the period, resulting in part from the issuance
of the 2.25%  Convertible  Subordinated  Debentures  and the 5.20% French Francs
Notes,  partially  offset by the  effect of higher  average  amounts of cash and
marketable securities invested during the period.

      Pretax profit margin was 10.1% in the third quarter of 1998 as compared to
9.8% in the same period in 1997.  Operating margin,  which excludes interest and
dividend income and interest expense,  was 11.3% in the third quarter of 1998 as
compared to 10.7% in the same period in 1997.

      The  effective  income tax rate was 42.4% in the third  quarter of 1998 as
compared to 40.9% in the third quarter of 1997. This increase primarily reflects
higher tax rates at the Company's international subsidiaries.

      The  increase  in equity in  affiliates  is the result of greater  profits
reported by certain  companies  in which the Company owns less than a 50% equity
interest.

      The  increase  in  minority  interest  expense  is  primarily  due  to new
minorities  resulting from  acquisitions and greater earnings by companies where
minority interests exist.


                                      -13-


                 MANAGEMENT'S DISCUSSION OF FINANCIAL CONDITION
                      AND RESULTS OF OPERATIONS (CONTINUED)

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

      Net income increased 29.6% in the third quarter of 1998 as compared to the
same period in 1997.  Absent the effect of net  acquisitions  and  movements  in
international  currency  exchange rates, net income increased 14.3% in the third
quarter of 1998 as compared to the third quarter of 1997.

Nine Months 1998 Compared to Nine Months 1997
- ---------------------------------------------

      Consolidated  worldwide  revenues from commission and fee income increased
29.8% in the first  nine  months of 1998  compared  to the same  period in 1997.
Consolidated  domestic revenues increased 28.8% in the first nine months of 1998
to $1,534.1  million  compared  to $1,190.9  million in the same period in 1997.
Consolidated  international revenues increased 30.9% in the first nine months of
1998 to $1,360.0  million  compared  to  $1,038.9  million in the same period in
1997.  Absent the effect of the net  acquisitions  of  subsidiary  companies and
movements in  international  currency  exchange  rates,  consolidated  worldwide
revenues  increased 16.2% in the first nine months of 1998 compared to the first
nine months of 1997.

      Operating  expenses  increased  28.5% in the first nine  months of 1998 as
compared to the same period in 1997. Excluding the effect of the net acquisition
activity and movements in international currency exchange rates mentioned above,
operating  expenses  increased  15.3% over 1997 levels.  


                                      -14-


                 MANAGEMENT'S DISCUSSION OF FINANCIAL CONDITION
                      AND RESULTS OF OPERATIONS (CONTINUED)

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

This  increase  reflects  normal salary  increases and growth in client  service
expenditures to support the increased revenue base.

      Net interest  expense  increased by $13.5 million in the first nine months
of 1998 as compared to the same period in 1997. This increase primarily reflects
higher average borrowings during the period, resulting in part from the issuance
of the 2.25%  Convertible  Subordinated  Debentures  and the 5.20% French Francs
Notes,  partially  offset by the  effect of higher  average  amounts of cash and
marketable securities invested during the period.

      Pretax  profit  margin  for the  first  nine  months  of 1998 was 12.3% as
compared to 11.7% in the same period in 1997.  Operating margin,  which excludes
interest and dividend income and interest  expense,  was 13.3% in the first nine
months of 1998 as compared to 12.4% in the same period in 1997.

      The  effective  income tax rate was 42.2% in the first nine months of 1998
as  compared  to 40.7% in the same  period  in  1997.  This  increase  primarily
reflects higher tax rates at the Company's international subsidiaries.

      Income  from  equity in  affiliates  for the first nine months of 1998 was
comparable to the same period in 1997.


                                      -15-


                 MANAGEMENT'S DISCUSSION OF FINANCIAL CONDITION
                      AND RESULTS OF OPERATIONS (CONTINUED)

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

      The  increase  in  minority  interest  expense  is  primarily  due  to new
minorities  resulting from  acquisitions and greater earnings by companies where
minority interests exist.

      Net income increased 28.9% in the first nine months of 1998 as compared to
the same period in 1997.  Absent the effect of net acquisitions and movements in
international  currency  exchange rates, net income increased 16.8% in the first
nine months of 1998 as compared to the same period in 1997.

Capital Resources and Liquidity
- -------------------------------

      Cash and cash  equivalents  at  September  30,  1998  decreased  to $313.2
million  from $556.4  million at December  31, 1997.  The  relationship  between
payables to the media and suppliers and receivables  from clients,  at September
30, 1998, is consistent with industry norms.

      The  Company  maintains  relationships  with a number of banks  worldwide,
which have extended unsecured committed lines of credit in amounts sufficient to
meet the Company's  cash needs.  At September  30, 1998,  the Company had $707.5
million  in such  unsecured  committed  lines of credit,  comprised  of a $500.0
million revolving credit agreement expiring June 30, 2003, and $207.5 million in
lines of credit, principally outside of the United States. Of the $707.5 million
in unsecured committed lines, $324.7 million remained available at September 30,
1998.


                                      -16-


                 MANAGEMENT'S DISCUSSION OF FINANCIAL CONDITION
                      AND RESULTS OF OPERATIONS (CONTINUED)

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

      On January 6, 1998, the Company issued  $230,000,000 of 2.25%  Convertible
Subordinated  Debentures  with a scheduled  maturity in 2013. The debentures are
convertible into common stock of the Company at a conversion price of $49.83 per
share subject to adjustment in certain events.  Debenture holders have the right
to require the Company to redeem the debentures on January 6, 2004 at a price of
118.968%,  or upon the  occurrence  of a Fundamental  Change,  as defined in the
indenture agreement,  at the prevailing redemption price. The Company may redeem
the  debentures,  as a whole or in part, on or after December 31, 2001 initially
at 112.841% and at increasing  prices  thereafter  to 118.968%  until January 6,
2004,  and 100%  thereafter.  Unless  the  debentures  are  redeemed,  repaid or
converted prior thereto,  the debentures will mature on January 6, 2013 at their
principal  amount.  The  proceeds  of this  issuance  are being used for general
corporate purposes, including working capital.

      On March 4, 1998, the Company issued  4,000,000 shares of common stock for
aggregate  proceeds  before  expenses  of  $171,400,000.  The  proceeds  of this
issuance are being used for general corporate purposes, including the funding of
the acquisition of GGT.

      On  June  24,  1998,  the  Company  issued  French  Francs   1,000,000,000
(approximately  $164 million at the June 24, 1998 exchange  rate) of 5.20% Notes
with a scheduled  maturity in 2005. The proceeds of this issuance are being used
for general corporate purposes.


                                      -17-


                 MANAGEMENT'S DISCUSSION OF FINANCIAL CONDITION
                      AND RESULTS OF OPERATIONS (CONTINUED)

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

      Management believes the aggregate lines of credit available to the Company
plus cash flows from  operations  will be adequate  to support  its  anticipated
requirements.

Year 2000 Issue
- ---------------

      The Year 2000 issue is the result of computer programs being written using
two digits, rather than four, to define the applicable year. Accordingly, any of
the computer programs utilized by the Company that have date sensitive  software
may cause system failures or miscalculations if data entry of "00" is recognized
as a date other than 2000.

      The  Company  has  developed  a  comprehensive  plan to address  Year 2000
issues.  This plan has included  the  establishment  of Omnicom  2000, a special
purpose entity  dedicated to ensuring that Omnicom  companies are addressing and
properly  resolving  Year 2000  compliance  issues.  Omnicom  2000  comprises an
Executive  Committee  of  senior  executives  from  Omnicom  and  its  principal
subsidiaries,  and a team  of  dedicated  internal  and  external  managers  and
consultants.  The Company's  comprehensive  plan includes an assessment phase, a
testing phase and an implementation phase.

      As part of its  assessment  phase,  the  Company  has  compiled a detailed
inventory  of systems and  potential  Year 2000  readiness  issues at all of its
principal locations. Based on this information,  the Company has determined that
it is required to modify  portions of its software so that its  


                                      -18-


                 MANAGEMENT'S DISCUSSION OF FINANCIAL CONDITION
                      AND RESULTS OF OPERATIONS (CONTINUED)

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

computer  systems  will  properly  utilize  dates beyond  December 31, 1999.  In
addition,   the  Company  is  dependent  on  third-party  computer  systems  and
applications,  particularly  with respect to such critical  tasks as accounting,
billing  and  buying,  planning  and  paying  for  media,  as well as on its own
computer systems and internally developed  applications.  The Company intends to
modify or replace all affected  systems,  and is also evaluating the adequacy of
the  processes  and  progress  of  third-party  vendors of  systems  that may be
affected by the Year 2000 issue. The Company believes that it has identified all
critical  third-party  vendors, and is currently testing and monitoring the Year
2000 readiness of such vendors.  The Company envisages that the testing phase of
its Year 2000 readiness plan will be substantially  completed by March 1999, and
that the implementation  phase will be substantially  completed by the middle of
1999.

      The  Company  believes  that,   through   upgrades,   modifications,   and
replacement  of its  existing  hardware,  software and non-IT  systems,  it will
achieve  Year 2000  readiness.  However,  if such  upgrades,  modifications  and
replacements  are not made,  or are not made in a timely  manner,  the Year 2000
issue could have a material impact on the Company's operations.

      Based on the Company's current estimates,  incremental out-of-pocket costs
of its Year 2000 program are expected to be immaterial in each of 1998 and 1999.
These  costs,  a portion of which will be  capitalizable,  include  third  party
consultants


                                      -19-


                 MANAGEMENT'S DISCUSSION OF FINANCIAL CONDITION
                      AND RESULTS OF OPERATIONS (CONTINUED)

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

and replacement and remediation of existing computer software and hardware. Such
costs do not  include  internal  management  time,  the effects of which are not
expected to be material to the  Company's  results of  operations  or  financial
condition. The Company will continue to refine its estimates of the costs of its
Year 2000 efforts,  through the update of reports from each location and through
the completion of its annual capital  expenditure budget review process.  To the
extent  applicable,  more detailed  information on costs will be included in the
Company's Annual Report on Form 10-K.

      At this stage of the process, the Company believes that it is difficult to
specifically  identify  the cause of the most  reasonable  worst  case Year 2000
scenario.  Due to  the  decentralized  nature  of the  Company's  structure  and
systems,  the Company  believes  that a  reasonable  worst case  scenario  would
involve the failures of significant third parties (including entities with which
the Company has no direct  involvement) that continue for more than several days
and  affect a  significant  number of the  Company's  operating  locations.  The
Company is considering  various contingency plans in the event of such failures.
The  development  of the  Company's  contingency  plans will be ongoing and will
reflect additional information with regard to third parties' Year 2000 readiness
as it is received.

      The Company's  Year 2000 efforts are ongoing and its overall plan, as well
as the  consideration  of  contingency  plans,  will  continue  to evolve as new
information becomes


                                      -20-


                 MANAGEMENT'S DISCUSSION OF FINANCIAL CONDITION
                      AND RESULTS OF OPERATIONS (CONTINUED)

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

available.  While the Company anticipates continuity of its business activities,
that  continuity  will be dependent  upon its ability,  and the ability of third
parties with whom the Company relies on directly, or indirectly, to be Year 2000
compliant.

Forward-Looking Statements

      This  "Management's  Discussion  of  Financial  Condition  and  Results of
Operations"   contains   disclosures  which  are   forward-looking   statements.
Forward-looking statements  include all statements that do not  relate solely to
historical or current  facts,  and can be identified by the use of words such as
"may," "will," "expect," "project," "estimate," "anticipate," "envisage," "plan"
or  "continue."  These  forward-looking  statements are based upon the Company's
current plans or expectations and are subject to a number of  uncertainties  and
risks that could significantly  affect current plans and anticipated actions and
the Company's  future financial  condition and results.  The  uncertainties  and
risks include, but are not limited to, general economic  conditions;  the impact
of competition in the marketing and communications  industry;  risks relating to
acquisition  activities;  the complexity of integrated computer systems; and the
success and expense of the remediation efforts of the Company,  its subsidiaries
and third parties in achieving Year 2000 compliance.  As a consequence,  current
plans, anticipated actions and future financial condition and results may differ
from those expressed in any  forward-looking  statements made by or on behalf of
the Company.


                                      -21-


                           PART II. OTHER INFORMATION

Item 6.  Exhibits

Exhibit Number            Description of Exhibit
- --------------            ----------------------
     27                   Financial Data Schedule (filed in electronic
                          format only)

SIGNATURES

      Pursuant to the  requirements of the Securities  Exchange Act of 1934, the
registrant  has duly  caused  this  report  to be  signed  on its  behalf by the
undersigned thereunto duly authorized.

                                                  Omnicom Group Inc.
                                                    (Registrant)

Date  November 13, 1998                        /s/  John D. Wren
                                               -----------------------------
                                               John D. Wren
                                               Chief Executive Officer
                                               and President

Date  November 13, 1998                        /s/  Jonathan E. Ramsden
                                               -----------------------------
                                               Jonathan E. Ramsden
                                               Controller
                                               (Principal Accounting Officer)


                                      -22-