SCHEDULE 14A INFORMATION
 
                  Proxy Statement Pursuant to Section 14(a) of
            the Securities Exchange Act of 1934 (Amendment No.    )
 
    Filed by the Registrant / /
    Filed by a Party other than the Registrant / /
 
    Check the appropriate box:
    / /  Preliminary Proxy Statement
    / /  Confidential, for Use of the Commission Only (as permitted by Rule
         14a-6(e)(2))
    / /  Definitive Proxy Statement
    /X/  Definitive Additional Materials
    / /  Soliciting Material Pursuant to Section240.14a-11(c) or
         Section240.14a-12
 
                        THE INTERPUBLIC GROUP OF COMPANIES, INC.
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                (Name of Registrant as Specified In Its Charter)
 
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    (Name of Person(s) Filing Proxy Statement, if other than the Registrant)
 
Payment of Filing Fee (Check the appropriate box):
 
/X/  No fee required.
/ /  Fee computed on table below per Exchange Act Rules 14a-6(i)(1)
     and 0-11.
     (1) Title of each class of securities to which transaction applies:
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     (2) Aggregate number of securities to which transaction applies:
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     (3) Per unit price or other underlying value of transaction computed
         pursuant to Exchange Act Rule 0-11 (set forth the amount on which the
         filing fee is calculated and state how it was determined):
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     (4) Proposed maximum aggregate value of transaction:
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     (5) Total fee paid:
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/ /  Fee paid previously with preliminary materials.
/ /  Check box if any part of the fee is offset as provided by Exchange Act Rule
     0-11(a)(2) and identify the filing for which the offsetting fee was paid
     previously. Identify the previous filing by registration statement number,
     or the Form or Schedule and the date of its filing.
     (1) Amount Previously Paid:
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     (2) Form, Schedule or Registration Statement No.:
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     (3) Filing Party:
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     (4) Date Filed:
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                    THE INTERPUBLIC GROUP OF COMPANIES, INC.
                          1271 AVENUE OF THE AMERICAS
                              NEW YORK, N.Y. 10020
 
                                                                     May 5, 1998
 
DEAR STOCKHOLDER:
 
    We have previously sent you proxy material relating to the Annual Meeting of
Stockholders to be held on Monday, May 18, 1998.
 
    According to our records, your proxy for this meeting has not yet been
received. Regardless of the number of shares you may own, it is important that
they be represented.
 
    Since the time remaining is short, we urge you to sign, date and mail the
enclosed proxy promptly.
 
                       Sincerely,
 
                       NICHOLAS J. CAMERA
                            SECRETARY
 
                 IF YOU HAVE ALREADY MAILED YOUR PROXY, PLEASE
                 ACCEPT OUR THANKS AND DISREGARD THIS REQUEST.