Exhibit 4.3

                                                               Execution Version

                          THIRD SUPPLEMENTAL INDENTURE

      This THIRD SUPPLEMENTAL INDENTURE (the "Supplemental Indenture") dated as
of November 4, 2004 among OMNICOM GROUP INC., a New York corporation (the
"Company"), OMNICOM CAPITAL INC., a Connecticut corporation ("OCI"), OMNICOM
FINANCE INC., a Delaware corporation ("OFI" and together with the Company and
OCI, the "Issuers"), and JPMORGAN CHASE BANK, as trustee under the indenture
referred to below (the "Trustee").

                              W I T N E S S E T H:

      WHEREAS, the Issuers and the Trustee have heretofore executed and
delivered to the Trustee an Indenture dated March 6, 2002, as amended by the
First Supplemental Indenture, dated February 13, 2004 and the Second
Supplemental Indenture dated August 12, 2004 (as so amended, the "Indenture"),
providing for the issuance of an aggregate principal amount of up to
$900,000,000 of Zero Coupon Zero Yield Convertible Notes due 2032 (the
"Securities"), all of which have been issued and $892,273,000 of which are
outstanding on the date hereof;

      WHEREAS, the Issuers desire to surrender their right under Section 3.08(b)
of the Indenture to elect to pay for Securities being purchased by the Issuers
pursuant to Section 3.08(a) of the Indenture with Common Stock;

      WHEREAS, it is in the best interests of the Issuers to surrender such
right;

      WHEREAS, Section 9.01(6) of the Indenture provides that the Issuers and
the Trustee may amend or supplement the Indenture without the consent of any
Securityholder to surrender any right, power or option conferred by this
Indenture on the Issuers;

      WHEREAS, an Opinion of Counsel and an Officer's Certificate have been
delivered to the Trustee under Section 9.06; and

      WHEREAS, pursuant to Sections 9.01 and 9.06 of the Indenture, the Trustee
and the Issuers are authorized to execute and deliver this Supplemental
Indenture;

      NOW THEREFORE, for good and valuable consideration, the receipt of which
is hereby acknowledged, the Issuers and the Trustee mutually covenant and agree
for the equal and ratable benefit of the holders of the Securities as follows:

      1. Definitions. All capitalized terms used but not defined herein shall
have the meanings given to such terms in the Indenture.

      2. Amendments. The Indenture be and hereby is amended as follows:

      2.1 Section 1.01 and Section 1.02 of the Indenture are hereby amended so
that the cross-references to the following definitions contained in Section 1.02
are deleted from Section 1.02 and such definitions are inserted in Section 1.01
in their proper alphabetical order as follows:


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            "cash" means U.S. legal tender;

            "Exchange Act" means the Securities Exchange Act of 1934, as
            amended; and

            "Securities Act" means the Securities Act of 1933, as amended.

      2.2 Section 1.02 of the Indenture is hereby amended so that the following
definitions are inserted in Section 1.02 in their proper alphabetical order as
follows:

                  "Issuers' Notice"...........3.08(c); and

                  "Issuers' Notice Date"....3.08(b).

      2.3 Section 1.02 of the Indenture is hereby amended so that the
cross-reference for the following definition is as follows:

                  "Purchase Party".............3.08(e).

      2.4 Section 1.02 and Section 12.08 of the Indenture are hereby amended so
that the reference to the defined terms "Company Notice," "Company Notice Date"
and "Market Price" are deleted from the aforementioned sections.

      2.5 Section 3.08 of the Indenture is hereby amended and restated in its
entirety to read as follows:

            "SECTION 3.08 Purchase of Securities at Option of the Holder. (a)
General. Subject to paragraph (e) below, if a Holder exercises its right to
require the Issuers to purchase Securities pursuant to paragraph 7 of the
Securities, such Securities shall be purchased by the Issuers or a Purchase
Party, if applicable, pursuant to paragraph 7 of the Securities on each July 31,
from July 31, 2003 through July 31, 2031 (each July 31 in the aforementioned
period, or, if July 31 in the applicable period is not a Business Day, the next
succeeding Business Day, a "Purchase Date"), at a purchase price equal to (i)
the Initial Principal Amount at Maturity of the Security for any Purchase Date
occurring prior to July 31, 2022 and (ii) the Initial Principal Amount at
Maturity plus accrued Contingent Additional Principal, if any, as of the
relevant Purchase Date for any Purchase Date occurring on or after July 31, 2022
through July 31, 2031 (each a "Purchase Price," as applicable), at the option of
the Holder thereof, upon:

            (1) delivery to the Paying Agent, by the Holder of a written notice
      of purchase (a "Purchase Notice") at any time from the opening of business
      on the date that is at least 20 Business Days prior to a Purchase Date
      until the close of business on the Purchase Date stating:

                  (A) the certificate number of the Security which the Holder
            will deliver to be purchased,

                  (B) the portion of the Initial Principal Amount at Maturity of
            the Security which the Holder will deliver to be purchased, which
            portion must be an


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            Initial Principal Amount at Maturity of at least $1,000 or an
            integral multiple thereof, and

                  (C) that such Security shall be purchased as of the Purchase
            Date pursuant to the terms and conditions specified in paragraph 7
            of the Securities and in this Indenture; and

            (2) delivery of such Security to the Paying Agent prior to, on or
      after the Purchase Date (together with all necessary endorsements) at the
      offices of the Paying Agent, such delivery being a condition to receipt by
      the Holder of the Purchase Price therefor; provided, however, that such
      Purchase Price shall be so paid pursuant to this Section 3.08 only if the
      Security so delivered to the Paying Agent shall conform in all respects to
      the description thereof in the related Purchase Notice, as determined by
      the Issuers.

            The Issuers or the Purchase Party, as applicable, shall purchase
from the Holder thereof, pursuant to this Section 3.08, a portion of a Security
if the Initial Principal Amount at Maturity of such portion is at least $1,000
or an integral multiple of $1,000. Provisions of this Indenture that apply to
the purchase of all of a Security also apply to the purchase of such portion of
such Security.

            Any purchase by the Issuers or the Purchase Party, as applicable,
contemplated pursuant to the provisions of this Section 3.08 shall be
consummated by the delivery of the cash consideration to be received by the
Holder (including accrued and unpaid Contingent Cash Interest, if any) on the
later of (i) the fourth Business Day following the applicable Purchase Date (the
"Payment Date") and (ii) the time of delivery of the Security.

            Notwithstanding anything herein to the contrary, any Holder
delivering to the Paying Agent the Purchase Notice contemplated by this Section
3.08(a) shall have the right to withdraw such Purchase Notice at any time prior
to the close of business on the Business Day following the Purchase Date by
delivery of a written notice of withdrawal to the Paying Agent in accordance
with Section 3.10.

            The Paying Agent shall promptly notify the Issuers and any Purchase
Party of the receipt by it of any Purchase Notice or written notice of
withdrawal thereof.

            (b) Purchase with Cash. On each Payment Date the Purchase Price of
Securities in respect of which a Purchase Notice pursuant to Section 3.08(a) has
been given, shall be paid by the Issuers or the Purchase Party, if any, with
cash equal to the aggregate Purchase Price of such Securities.

            (c) The Issuers' Notice. The Issuers shall send a notice (the
"Issuers' Notice") to the Holders (and to beneficial owners as required by
applicable law) in the manner provided in Section 12.02 not less than 20
Business Days prior to the applicable Purchase Date (the "Issuers' Notice
Date"). Each Issuers' Notice shall include a form of Purchase Notice to be
completed by a Securityholder and shall state:


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            (i) the Purchase Price, the Conversion Rate and, to the extent known
      at the time of such notice, the amount of Contingent Cash Interest, if
      any, that will be accrued and payable with respect to the Securities as of
      the Purchase Date;

            (ii) the name and address of the Paying Agent and the Conversion
      Agent;

            (iii) that Securities as to which a Purchase Notice has been given
      may be converted pursuant to Article 10 hereof only if the applicable
      Purchase Notice has been withdrawn in accordance with the terms of this
      Indenture;

            (iv) that Securities must be surrendered to the Paying Agent to
      collect payment of the Purchase Price and Contingent Cash Interest, if
      any;

            (v) that the Purchase Price for any Security as to which a Purchase
      Notice has been given and not withdrawn, together with any accrued
      Contingent Cash Interest payable with respect thereto, will be paid on the
      later of the Payment Date and the time of surrender of such Security as
      described in (iv);

            (vi) the procedures the Holder must follow to exercise rights under
      Section 3.08 and a brief description of those rights;

            (vii) briefly, the conversion rights of the Securities;

            (viii) the procedures for withdrawing a Purchase Notice (including,
      without limitation, for a conditional withdrawal pursuant to the terms of
      Section 3.10);

            (ix) that, unless the Issuers default in making payment of such
      Purchase Price, Contingent Additional Principal and Contingent Cash
      Interest, if any, on Securities called for redemption will cease to accrue
      in favor of the Holder surrendering such Securities immediately after the
      Purchase Date; and

            (x) the CUSIP number of the Securities.

            At the Issuers' request, the Trustee shall give such Issuers' Notice
in the Issuers' name and at the Issuers' expense; provided, however, that, in
all cases, the text of such Issuers' Notice shall be prepared by the Issuers and
may include such other information, if any, as the Issuers deem appropriate so
long as it is consistent with this Indenture.

            (d) Procedure upon Purchase. The Issuers or the Purchase Party, if
any, shall deposit cash at the time and in the manner as provided in Section
3.11, sufficient to pay the aggregate Purchase Price of, and any accrued and
unpaid Contingent Cash Interest with respect to, all Securities to be purchased
pursuant to this Section 3.08.

            (e) The Issuers shall have the option, exercisable at any time or
from time to time, by an instrument in writing signed by the Issuers and
provided to the Paying Agent, to designate a, or change the existing designation
of the, financial institution to which Securities surrendered by a Holder for
purchase will be initially offered by the Paying Agent on behalf of a Holder for
purchase (a "Purchase Party"). If applicable, the Issuers shall enter into an
agreement


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with the Paying Agent, in form and substance reasonably satisfactory to the
Paying Agent, providing that, at the opening of business on each Business Day
during the period commencing 20 Business Days prior to the Purchase Date through
the Payment Date, the Paying Agent shall inform the Purchase Party as to the
aggregate Initial Principal Amount at Maturity of Securities surrendered for
purchase on the prior Business Day. The Purchase Party may accept for purchase
all or any of such Securities if it agrees, no later than the time specified in
the agreement between the Issuers and the Paying Agent (or, absent such
agreement, by the Payment Date), to deliver in payment therefor the Purchase
Price. Settlement of any such purchase shall take place no later than the
Payment Date. In the event that the Purchase Party fails to deliver the Purchase
Price by such Payment Date, the Purchase Party shall be in default of its
obligations and, instead of being purchased by the Purchase Party, the
Securities will be purchased by the Issuers in accordance with Section 3.08(d).
A Holder whose Securities are purchased in whole or in part shall be given a
written confirmation from the Paying Agent informing such Holder as to the
aggregate Principal Amount at Maturity of the Securities so purchased. The
agreement between the Issuers and the Paying Agent setting forth the procedures
to be followed in a purchase may be changed at any time by the Issuers and the
Paying Agent so long as such change does not, as evidenced by an Opinion of
Counsel delivered to the Paying Agent, adversely affect the rights under this
Indenture of a Holder who surrenders its Securities for purchase."

      2.6 Section 3.10 of the Indenture is hereby amended and restated in its
entirety to read as follows:

            "SECTION 3.10 Effect of Purchase Notice or Change in Control
Purchase Notice. Upon receipt by the Paying Agent of the Purchase Notice or
Change in Control Purchase Notice specified in Section 3.08(a) or Section
3.09(c), as applicable, the Holder of the Security in respect of which such
Purchase Notice or Change in Control Purchase Notice, as the case may be, was
given shall (unless such Purchase Notice or Change in Control Purchase Notice is
withdrawn as specified in the following two paragraphs) thereafter be entitled
to receive solely the Purchase Price or Change in Control Purchase Price, as the
case may be, and any accrued and unpaid Contingent Cash Interest, with respect
to such Security through the Purchase Date or Change in Control Purchase Date,
as applicable. Such Purchase Price or Change in Control Purchase Price and
Contingent Cash Interest, if any, shall be paid to such Holder, subject to
receipts of funds and/or securities by the Paying Agent, promptly following the
later of (x) the Purchase Date or the Change in Control Purchase Date, as the
case may be, with respect to such Security (provided the conditions in Section
3.08(a) or Section 3.09(c), as applicable, have been satisfied) and (y) the time
of delivery of such Security to the Paying Agent by the Holder thereof in the
manner required by Section 3.08(a) or Section 3.09(c), as applicable. Securities
in respect of which a Purchase Notice or Change in Control Purchase Notice, as
the case may be, has been given by the Holder thereof may not be converted
pursuant to Article 10 hereof on or after the date of the delivery of such
Purchase Notice or Change in Control Purchase Notice, as the case may be, unless
such Purchase Notice or Change in Control Purchase Notice, as the case may be,
has first been validly withdrawn as specified in the following two paragraphs.

            A Purchase Notice or Change in Control Purchase Notice, as the case
may be, may be withdrawn by means of a written notice of withdrawal delivered to
the office of the Paying Agent in accordance with the Purchase Notice or Change
in Control Purchase Notice, as


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the case may be, at any time prior to the close of business on the Purchase Date
or the Change in Control Purchase Date, as the case may be, specifying:

            (1) the certificate number of the Security in respect of which such
      notice of withdrawal is being submitted,

            (2) the Initial Principal Amount at Maturity of the Security with
      respect to which such notice of withdrawal is being submitted, and

            (3) the Initial Principal Amount at Maturity, if any, of such
      Security which remains subject to the original Purchase Notice or Change
      in Control Purchase Notice, as the case may be, and which has been or will
      be delivered for purchase by the Issuers.

            There shall be no purchase of any Securities pursuant to Section
3.08 or 3.09 if there has occurred (prior to, on or after, as the case may be,
the giving, by the Holders of such Securities, of the required Purchase Notice
or Change in Control Purchase Notice, as the case may be) and is continuing an
Event of Default (other than a default in the payment of the Purchase Price or
Change in Control Purchase Price, as the case may be, and any accrued and unpaid
Contingent Cash Interest with respect to such Securities). The Paying Agent will
promptly return to the respective Holders thereof any Securities (x) with
respect to which a Purchase Notice or Change in Control Purchase Notice, as the
case may be, has been withdrawn in compliance with this Indenture, or (y) held
by it during the continuance of an Event of Default (other than a default in the
payment of the Purchase Price or Change in Control Purchase Price, as the case
may be, and any accrued and unpaid Contingent Cash Interest with respect to such
Securities) in which case, upon such return, the Purchase Notice or Change in
Control Purchase Notice with respect thereto shall be deemed to have been
withdrawn."

      2.7 The second paragraph of Section 7 of Exhibit A-1 to the Indenture is
hereby amended and restated in its entirety to read as follows:

      "The Purchase Price shall be paid in cash and shall be paid by a Purchase
Party if so designated by the Issuers, in accordance with the terms of the
Indenture."

      3. Separability Clause. In case any provision in this Supplemental
Indenture shall be invalid, illegal or unenforceable, the validity, legality and
enforceability of the remaining provisions shall not in any way be affected or
impaired thereby.

      4. Modification, Amendment and Waiver. The provisions of this Supplemental
Indenture may not be amended, supplemented, modified or waived except by a
execution of a Supplemental Indenture executed by the Issuers, and, to the
extent such amendment, supplement or waiver limits or impairs the rights of any
Securityholder, by such Securityholder. Any such amendment shall comply with
Article 9 of the Indenture. Until an amendment, waiver or other action by
Securityholders becomes effective, a consent thereto by a Securityholder of a
Security hereunder is a continuing consent by the Securityholder and every
subsequent Securityholder of that Security or portion of the Security that
evidences the same obligation as the consenting Securityholder's Security, even
if notation of the consent, waiver or action is not made on the Security.
However, any such Securityholder or subsequent Securityholder may revoke the
consent, waiver or action as to such Securityholder's Security or portion of the
Security if the


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Trustee receives the notice of revocation before the date the amendment, waiver
or action becomes effective. After an amendment, waiver or action becomes
effective, it shall bind every Securityholder.

      5. Ratification of Indenture; Supplemental Indenture Part of Indenture.
Except as expressly amended hereby, the Indenture is in all respects ratified
and confirmed and all the terms, conditions and provisions thereof shall remain
in full force and effect. In the event of a conflict between the terms and
conditions of the Indenture and the terms and conditions of this Supplemental
Indenture, then the terms and conditions of this Supplemental Indenture shall
prevail. This Supplemental Indenture shall form a part of the Indenture for all
purposes, and every holder of Securities heretofore or hereafter authenticated
and delivered shall be bound hereby.

      6. Trust Indenture Acts Controls. If any provision of this Supplemental
Indenture limits, qualifies or conflicts with any provision of the Trust
Indenture Act of 1939, as amended ("TIA"), that is required under the TIA to be
part of and govern any provision of this Supplemental Indenture, the provision
of the TIA shall control. If any provision of this Supplemental Indenture
modifies or excludes any provisions of the TIA that may be so modified or
excluded, the provisions of the TIA shall be deemed to apply to the Indenture as
so modified or to be excluded by this Supplemental Indenture, as the case may
be.

      7. Governing Law. THIS SUPPLEMENTAL INDENTURE SHALL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK, AS APPLIED TO
CONTRACTS MADE AND PERFORMED WITHIN THE STATE OF NEW YORK WITHOUT GIVING EFFECT
TO THE PRINCIPLES OF CONFLICTS OF LAW.

      8. Trustee Makes No Representation. The statements herein are deemed to be
those of the Company, OCI or OFI, as applicable. The Trustee makes no
representation as to the validity or sufficiency of this Supplemental Indenture.

      9. Multiple Originals. The parties may sign any number of copies of this
Supplemental Indenture. Each signed copy shall be an original, but all of them
together represent the same agreement. One signed copy is enough to prove this
Supplemental Indenture.

      10. Effect of Headings. The Section headings herein are for convenience
only and shall not effect the construction thereof.

      11. Notices. Any request, demand, authorization, notice, waiver, consent
or communication to any of the parties shall be made as set forth in Section
12.02 of the Indenture, as said Section may be amended hereby.

      12. Successors. All agreements of each of the Company, OCI and OFI in
respect of this Supplemental Indenture shall bind its successor.


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      IN WITNESS WHEREOF, this Supplemental Indenture has been duly executed by
the Company, OCI, OFI and the Trustee as of the date first written above.

                                         OMNICOM GROUP INC.

                                         By: /s/ Randall J. Weisenburger
                                             -----------------------------------
                                             Name:  Randall J. Weisenburger
                                             Title: Executive Vice President and
                                                    Chief Financial Officer

                                         OMNICOM CAPITAL INC.

                                         By: /s/ Michael J. O'Brien
                                             -----------------------------------
                                             Name:  Michael J. O'Brien
                                             Title: Secretary

                                         OMNICOM FINANCE INC.

                                         By: /s/ Randall J. Weisenburger
                                             -----------------------------------
                                             Name:  Randall J. Weisenburger
                                             Title: Chief Executive Officer

                                         JPMORGAN CHASE BANK, as Trustee

                                         By: /s/ Carol Ng
                                             -----------------------------------
                                             Name:  Carol Ng
                                             Title: Vice President


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