Exhibit 4.1

                                                               Execution Version

                          SECOND SUPPLEMENTAL INDENTURE

      This SECOND SUPPLEMENTAL INDENTURE (the "Supplemental Indenture") dated as
of August 12, 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, 2003 (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 (i) to surrender their right to pay
Securityholders who are converting their Securities pursuant to Article 10 of
the Indenture with shares of Common Stock, (ii) to surrender their right to
designate a financial institution to deliver shares of Common Stock upon
conversion pursuant to Article 10 of the Indenture and (iii) to modify the
method by which Contingent Cash Interest is determined;

      WHEREAS, it is in the best interests of the Issuers to surrender such
rights and to modify the method by which Contingent Cash Interest is determined;

      WHEREAS, Sections 9.02(2) and 9.02(5) of the Indenture provides that the
Issuers and the Trustee may amend or supplement the Indenture only with the
consent of affected Securityholders;

      WHEREAS, all Securityholders have consented to this Supplemental Indenture
and all outstanding Notes shall be bound by it;

      WHEREAS, an Opinion of Counsel has been delivered to the Trustee under
Section 9.02; and

      WHEREAS, pursuant to Sections 9.02 and 9.06 of the Indenture, the Trustee
and the Company 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 set forth in the Indenture.

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


<PAGE>

      2.1   Section 10.02 of the Indenture is hereby amended and restated in its
            entirety to read as follows:

            "SECTION 10.02 Conversion Procedure.

      To convert a Security a Holder must satisfy the requirements in paragraph
9 of the Securities. The date on which the Holder satisfies all those
requirements is the conversion date (the "Conversion Date").

      As soon as practicable following the Conversion Date, the Issuers will
deliver, directly or through the Conversion Agent, an amount in cash (the "Cash
Amount") equal to the Initial Principal Amount at Maturity of the Securities
surrendered for conversion. The difference, if positive, between the Conversion
Value and the Initial Principal Amount at Maturity of the Securities surrendered
for conversion (the "Premium") may be satisfied, at the option of the Issuers,
exercisable at any time or from time to time, by an instrument in writing signed
by the Issuers, by delivering to a Converting Holder, in addition to the Cash
Amount, either (i) an amount in cash equal to the Premium or (ii) the number of
whole shares of Common Stock equal to the quotient of (x) the Premium for such
Securities divided by (y) the last reported Sales Price of the Company's Common
Stock on the Conversion Date (if the Conversion Date is not a Business Day, then
on the Business Day immediately preceding the Conversion Date), plus a cash
payment for fractional shares determined pursuant to Section 10.03. At any time
after which the Securities could be converted by action of the Holder, at the
written request of a Holder, the Company will, within five calendar days of
receipt of such request, notify such Holder whether the Premium will be
satisfied in cash or Company Common Stock as aforesaid. Any such notice by the
Company will be irrevocable for 60 calendar days (or such longer period as the
Company may specify on the notice), and then may only be revoked after ten
additional calendar days notice. All elections or notices contemplated to be
given by the Company in this paragraph will be made or given by delivery of
written notice to the Trustee as herein provided and to the Holder.

      In the event that the Issuers elect to satisfy the Premium with Common
Shares, the person in whose name the certificate is registered shall be treated
as a stockholder of record on and after the Conversion Date; provided, however,
that no surrender of a Security on any date when the stock transfer books of the
Company shall be closed shall be effective to constitute the person or persons
entitled to receive the shares of Common Stock upon such conversion as the
record holder or holders of such shares of Common Stock on such date, but such
surrender shall be effective to constitute the person or persons entitled to
receive such shares of Common Stock as the record holder or holders thereof for
all purposes at the close of business on the next succeeding day on which such
stock transfer books are open; such conversion shall be at the Conversion Rate
in effect on the date that such Security shall have been surrendered for
conversion, as if the stock transfer books of the Company had not been closed.

      Upon conversion of a Security, such person shall no longer be a Holder of
such Security.

      No payment or adjustment will be made for dividends on, or other
distributions with respect to, any Common Stock except as provided in this
Article 10. On conversion of a Security, that portion of accrued Contingent
Additional Principal attributable to the period from


                                      -2-
<PAGE>

the Issue Date of the Security through the Conversion Date and (except as
provided below) accrued Contingent Cash Interest with respect to the converted
Security through the Conversion Date shall not be cancelled, extinguished or
forfeited, but rather shall be deemed to be paid in full to the Holder thereof
through delivery of the Cash Amount, together with cash or Common Stock in
respect of the Premium, in exchange for the Security being converted pursuant to
the provisions hereof; and the fair market value of such cash or Common Stock in
respect of the Premium shall be treated as delivered, to the extent thereof,
first in exchange for Contingent Additional Principal accrued through the
Conversion Date and accrued Contingent Cash Interest, and the Cash Amount shall
be treated as delivered in exchange for the Initial Principal Amount at Maturity
of the Security being converted pursuant to the provisions hereof.

      If the Holder converts more than one Security at the same time, the Cash
Amount, together with the cash or Common Stock in respect of the Premium,
issuable upon the conversion shall be based on the total Principal Amount at
Maturity of the Securities converted.

      If the last day on which a Security may be converted is a Legal Holiday,
the Security may be surrendered on the next succeeding day that is not a Legal
Holiday.

      Upon surrender of a Security that is converted in part, the Issuers shall
execute, and the Trustee shall authenticate and deliver to the Holder, a new
Security in an authorized denomination equal in Principal Amount at Maturity to
the unconverted portion of the Security surrendered."

      2.2   Section 10.05 of the Indenture is hereby amended and restated in its
            entirety to read as follows:

            "SECTION 10.05 Company to Provide Stock.

      The Company shall, prior to issuance of any Securities under this Article
10, and from time to time as may be necessary, reserve out of its authorized but
unissued Common Stock a sufficient number of shares of Common Stock to permit
satisfaction of the Premium with Common Stock upon the conversion of the
Securities.

      All shares of Common Stock delivered upon conversion of the Securities
shall be duly authorized, validly issued, fully paid and nonassessable and free
from preemptive rights and any lien or adverse claim.

      The Company will endeavor promptly to comply with all federal and state
securities laws regulating the offer and delivery of shares of Common Stock upon
conversion of Securities, if any, and will list or cause to have quoted such
shares of Common Stock on each national securities exchange or in the
over-the-counter market or such other market on which the Common Stock is then
listed or quoted."


                                      -3-
<PAGE>

      2.3   A new subparagaph (d), to read in its entirety as follows, will be
            added to the existing Section 10.08 of the Indenture:

            SECTION 10.08 Adjustment for Other Distributions.

      "(d) if the Company pays any Regular Cash Dividend during any quarterly
fiscal period for which Contingent Cash Interest is payable, the Conversion Rate
will be adjusted as of the record date for such Regular Cash Dividend based on
the following formula:

                               CR' = CR0 x   SP0
                                          ---------
                                           SP0 - C

      CR0 = the Conversion Rate in effect immediately prior to the record date
            for such Regular Cash Dividend

      CR' = the Conversion Rate in effect immediately after the record date
            for such Regular Cash Dividend; provided that (1) CR' shall not be
            less than 9.09 (except as adjusted pursuant to other provisions of
            this Indenture); and (2) when, if not for clause (1) CR' would be
            less than 9.09, CR0 will be equal to such CR' for purposes of making
            the next quarterly adjustment calculation.

      SP0 = the average of the last reported Sale Prices of the Common Stock
            for the ten consecutive Trading Days prior to the Business Day
            immediately preceding the record date of such Regular Cash Dividend

      C   = the difference of (x) the amount in cash per share paid to holders
            of Common Stock in any quarterly period minus (y) the amount set
            forth for such quarterly fiscal period in Section 5 of the Notes
            divided by 9.09 (appropriately adjusted from time to time for any
            share dividends on, or subdivisions of, the Common Stock)

      Notice of any adjustment to the Conversion Rate as provided in this
Section 10.08(d) need not be given to any Holder unless such adjustment,
together with all prior adjustments pursuant to this Section 10.08(d) for which
notice has not previously been given, would require an increase or decrease of
at least 1% in the Conversion Rate; provided that the Company shall give Holders
annual notice, within 120 days after the end of each fiscal year of the Company
(beginning with the fiscal year ending on December 31, 2007), of all adjustments
made pursuant to this Section 10.08(d) during such fiscal year.

      "Regular Cash Dividends" means quarterly or other periodic cash dividends
on the Company's Common Stock as declared by the Board of Directors as part of
its cash dividend payment practices and that are not designated by the Board of
Directors as extraordinary or special or other nonrecurring dividends."


                                      -4-
<PAGE>

      2.4   Section 10.09 of the Indenture is hereby amended and restated in its
            entirety to read as follows:

            "SECTION 10.09 When Adjustment May Be Deferred.

      "Except for adjustments calculated pursuant to Section 10.08(d), no
adjustment in the Conversion Rate need be made unless the adjustment would
require an increase or decrease of at least 1% in the Conversion Rate. Any
adjustments that are not made shall be carried forward and taken into account in
any subsequent adjustment."

      2.5   Section 5 of Exhibit A-1 to the Indenture is hereby amended and
            restated in its entirety to read as follows:

            "5. Contingent Cash Interest.

      Subject to the record date provisions specified in this paragraph 5, the
Issuers shall pay contingent cash interest ("Contingent Cash Interest") to the
Holder of this Security during any six-month period (each a "Contingent Interest
Period") from August 1 to January 31 or from February 1 to July 31, commencing
on or after August 1, 2007, if the average of the Zero Coupon Zero Yield
Convertible Note Market Prices for each of the days in the Five-Day Period with
respect to such Contingent Interest Period equals or exceeds 120% of the Initial
Principal Amount at Maturity of this Security.

      Contingent Cash Interest, if any, will accrue from the first day of the
applicable six-month period and be payable quarterly on January 31, April 30,
July 31 and October 31 (each a "Contingent Interest Payment Date") of the
relevant six-month period to Holders of the Security on the record date, which
will be each October 15, January 15, April 15 and July 15 immediately preceding
each applicable payment date set forth below.

      For any six-month period, the amount of Contingent Cash Interest payable
on any Contingent Interest Payment Date per $1,000 Initial Principal Amount at
Maturity thereof in respect of any Contingent Interest Period shall equal the
amounts set forth below per $1,000 Initial Principal Amount at Maturity for each
applicable six-month period.

<TABLE>
<CAPTION>
Payment Date                         Quarterly Interest    Payment Date                      Quarterly Interest
<S>                                         <C>            <C>                                      <C>
October 31, 2007...............             $2.11          April 30, 2020.................          $3.51
January 31, 2008...............             $2.11          July 31, 2020..................          $3.51
April 30, 2008.................             $2.11          October 31, 2020...............          $3.63
July 31, 2008..................             $2.11          January 31, 2021...............          $3.63
October 31, 2008...............             $2.22          April 30, 2021.................          $3.63
January 31, 2009...............             $2.22          July 31, 2021..................          $3.63
April 30, 2009.................             $2.22          October 31, 2021...............          $3.75
July 31, 2009..................             $2.22          January 31, 2022...............          $3.75
October 31, 2009...............             $2.34          April 30, 2022.................          $3.75
January 31, 2010...............             $2.34          July 31, 2022..................          $3.75
April 30, 2010.................             $2.34          October 31, 2022...............          $3.86
July 31, 2010..................             $2.34          January 31, 2023...............          $3.86
October 31, 2010...............             $2.46          April 30, 2023.................          $3.86
January 31, 2011...............             $2.46          July 31, 2023..................          $3.86
</TABLE>

                                      -5-
<PAGE>
<TABLE>
<CAPTION>
Payment Date                         Quarterly Interest    Payment Date                      Quarterly Interest
<S>                                         <C>            <C>                                      <C>
April 30, 2011.................             $2.46          October 31, 2023...............          $3.98
July 31, 2011..................             $2.46          January 31, 2024...............          $3.98
October 31, 2011...............             $2.57          April 30, 2024.................          $3.98
January 31, 2012...............             $2.57          July 31, 2024..................          $3.98
April 30, 2012.................             $2.57          October 31, 2024...............          $4.10
July 31, 2012..................             $2.57          January 31, 2025...............          $4.10
October 31, 2012...............             $2.69          April 30, 2025.................          $4.10
January 31, 2013...............             $2.69          July 31, 2025..................          $4.10
April 30, 2013.................             $2.69          October 31, 2025...............          $4.21
July 31, 2013..................             $2.69          January 31, 2026...............          $4.21
October 31, 2013...............             $2.81          April 30, 2026.................          $4.21
January 31, 2014...............             $2.81          July 31, 2026..................          $4.21
April 30, 2014.................             $2.81          October 31, 2026...............          $4.33
July 31, 2014..................             $2.81          January 31, 2027...............          $4.33
October 31, 2014...............             $2.93          April 30, 2027.................          $4.33
January 31, 2015...............             $2.93          July 31, 2027..................          $4.33
April 30, 2015.................             $2.93          October 31, 2027...............          $4.45
July 31, 2015..................             $2.93          January 31, 2028...............          $4.45
October 31, 2015...............             $3.04          April 30, 2028.................          $4.45
January 31, 2016...............             $3.04          July 31, 2028..................          $4.45
April 30, 2016.................             $3.04          October 31, 2028...............          $4.56
July 31, 2016..................             $3.04          January 31, 2029...............          $4.56
October 31, 2016...............             $3.16          April 30, 2029.................          $4.56
January 31, 2017...............             $3.16          July 31, 2029..................          $4.56
April 30, 2017.................             $3.16          October 31, 2029...............          $4.68
July 31, 2017..................             $3.16          January 31, 2030...............          $4.68
October 31, 2017...............             $3.28          April 30, 2030.................          $4.68
January 31, 2018...............             $3.28          July 31, 2030..................          $4.68
April 30, 2018.................             $3.28          October 31, 2030...............          $4.80
July 31, 2018..................             $3.28          January 31, 2031...............          $4.80
October 31, 2018...............             $3.39          April 30, 2031.................          $4.80
January 31, 2019...............             $3.39          July 31, 2031..................          $4.80
April 30, 2019.................             $3.39          October 31, 2031...............          $4.92
July 31, 2019..................             $3.39          January 31, 2032...............          $4.92
October 31, 2019...............             $3.51          April 30, 2032.................          $4.92
January 31, 2020...............             $3.51          July 31, 2032..................          $4.92
</TABLE>

      "Five-Day Period" means, with respect to any Contingent Interest Period,
the five trading days ending on the second trading day immediately preceding the
first day of such Contingent Interest Period; provided, however, that if the
Company shall have declared a Regular Cash Dividend on its Common Stock that is
payable during such Contingent Interest Period but for which the record date for
determining stockholders entitled thereto precedes the first day of such
Contingent Interest Period, then "Five-Day Period" shall mean, with respect to
such Contingent Interest Period, the five trading days ending on the second
trading day immediately preceding such record date.

      "Regular Cash Dividends" means quarterly or other periodic cash dividends
on the Company's Common Stock as declared by the Board of Directors as part of
its cash dividend payment practices and that are not designated by the Board of
Directors as extraordinary or special or other nonrecurring dividends.

      "Zero Coupon Zero Yield Convertible Note Market Price" means, as of any
date of determination, the average of the secondary market bid quotations per
$1,000 Principal


                                      -6-
<PAGE>

Amount at Maturity obtained by the Bid Solicitation Agent for $10 million
Principal Amount at Maturity of Securities at approximately 4:00 p.m., New York
City time, on such determination date from three independent nationally
recognized securities dealers in The City of New York (none of which shall be an
Affiliate of the Issuers) selected by the Issuers; provided, however, if (a) at
least three such bids are not obtained by the Bid Solicitation Agent or (b) in
the Issuers' reasonable judgment, the bid quotations are not indicative of the
secondary market value of the Securities as of such determination date, then the
Zero Coupon Zero Yield Convertible Note Market Price for such determination date
shall equal (i) the Conversion Rate in effect as of such determination date
multiplied by (ii) the average of the Sale Prices of the Common Stock for each
of the five trading days ending on such determination date, appropriately
adjusted to take into account the occurrence, during the period commencing on
the first of such trading days during such five trading day period and ending on
such determination date, of any event described in Section 10.06, 10.07 or 10.08
(subject to the conditions set forth in Sections 10.09 and 10.10) of the
Indenture.

      The Issuers will determine every six months, commencing August 1, 2007,
whether the conditions to the payment of Contingent Cash Interest have been
satisfied and, if so, the Issuers shall promptly notify the Holders of this
Security of such determination and shall use their reasonable best efforts to
post this information on their web site or, at their option, otherwise publicly
disclose this information."

      2.6   Section 9 of Exhibit A-1 to the Indenture is hereby amended and
            restated in its entirety to read as follows:

"9. Conversion.

      Holders may surrender Securities for conversion only if at least one of
the conditions described in (a) through (d) below is satisfied. In addition, a
Security for which a Holder has delivered a Purchase Notice or a Change in
Control Purchase Notice requiring the Issuers to purchase the Security may be
surrendered for conversion only if such notice is withdrawn in accordance with
the Indenture.

      The initial Conversion Rate is 9.09 shares per $1,000 Initial Principal
Amount at Maturity of a Security, subject to adjustment upon the occurrence of
certain events described in the Indenture. A Holder otherwise entitled to a
fractional share will receive cash in an amount equal to the value of such
fractional share based on the Sale Price on the trading day immediately
preceding the Conversion Date.

      The ability to surrender Securities for conversion will expire at the
close of business on July 31, 2032.

      (a) Before July 31, 2022, Holders may surrender a Security for conversion
at the then-applicable conversion price during any calendar quarter, commencing
after March 31, 2002 if the average Conversion Values of the Security for each
of the last 20 trading days in the preceding calendar quarter is greater than or
equal to a specified percentage of the Initial Principal Amount at Maturity;
125% for the quarter ending June 30, 2002, and increasing 5% per quarter for
each quarter thereafter up to a maximum of 220% of the Initial Principal Amount
at


                                      -7-
<PAGE>

Maturity of the Security for the quarter ending June 30, 2007. Thereafter, this
percentage shall remain at 220%. If the foregoing condition is satisfied at any
time after July 31, 2003 and before July 31, 2022, then the Securities will
become and remain convertible at any time thereafter at the option of the
Holder, through maturity. On or after July 31, 2022, Holders may surrender a
Security for conversion during any calendar quarter if the average of the
Conversion Values of the Security for each of the last 20 trading days in the
preceding calendar quarter is greater than or equal to 110% of the Principal
Amount at Maturity of the Security. If the foregoing condition is satisfied,
then the Securities will become and remain convertible at any time thereafter at
the option of the Holder, through maturity.

      (b) Holders may also surrender a Security for conversion at the
then-applicable conversion price at any time after the credit rating assigned to
the Securities is reduced to Baa3 or lower by Moody's Investors Service, Inc. or
BBB or lower by Standard & Poor's Ratings Services, even if the credit rating
assigned has subsequently been changed to a higher rating.

      (c) A Holder may surrender for conversion at the then-applicable
conversion price a Security with respect to which the Issuers have mailed a
Redemption Notice at any time prior to the close of business on the second
Business Day prior to the Redemption Date, even if it is not otherwise
convertible at that time.

      (d) If the Company elects to

   o  distribute to all Holders of Common Stock certain rights entitling them to
      purchase, for a period expiring within 60 days, Common Stock at less than
      the Sale Price at the time, or

   o  distribute to all Holders of Common Stock assets, debt securities or
      certain rights to purchase securities of the Company, which distribution
      has a per share value as determined by the Company's Board of Directors
      exceeding 15% of the closing price of the Common Stock on the day
      preceding the declaration date for such distribution,

the Company must notify the Holders of Securities at least 20 days prior to the
Ex-Dividend Date for such distribution. Once the Company has given such notice,
Holders may surrender their Securities for conversion at the then-applicable
conversion price at any time thereafter until the earlier of the close of
business on the Business Day prior to the Ex-Dividend Date or the Company's
announcement that such distribution will not take place.

      Contingent Cash Interest will not be paid on Securities that are
converted; provided, however that Holders of Securities surrendered for
conversion during the period from the close of business on any record date for
determining an obligation to pay Contingent Cash Interest to the opening of
business on the date on which such Contingent Cash Interest is payable, shall be
entitled to receive such Contingent Cash Interest on the date on which such
Contingent Cash Interest is payable. Except Securities with respect to which the
Issuers have mailed a Notice of Redemption, Securities surrendered for
conversion during such periods must be accompanied by


                                      -8-
<PAGE>

payment of an amount equal to the Contingent Cash Interest with respect thereto
that the registered Holder is to receive.

      The Conversion Rate will not be adjusted for accrued Contingent Additional
Principal, if any, or Contingent Cash Interest, if any. As soon as practicable
following the Conversion Date, the Issuers will deliver through the Conversion
Agent, the Cash Amount, together with cash or a certificate for the number of
full shares of Common Stock into which the Premium of any Security is converted,
together with and any cash payment for fractional shares. Delivery to the Holder
of the Cash Amount, together with such cash or shares of Common Stock
deliverable in connection with the Premium, will be deemed to satisfy the
Issuers' obligation to pay the Principal Amount at Maturity of and any accrued
Contingent Additional Principal on the Security.

      Subject to the provisions of this paragraph 9 and notwithstanding the fact
that any other condition to conversion has not been satisfied, in the event the
Company is a party to a consolidation, merger or binding share exchange pursuant
to which the Common Stock would be converted into cash, securities or other
property as set forth in Section 10.14 of the Indenture, the Securities may be
surrendered for conversion at any time from and after the date which is 15 days
prior to the date the Company announces the anticipated effective time until 15
days after the actual effective date of such transaction, and at the effective
time of such transaction the right to convert a Security into Common Stock will
be deemed to have changed into a right to convert it into the kind and amount of
cash, securities or other property which the Holder would have received if the
Holder had converted its Security immediately prior to the transaction. If the
transaction also constitutes a Change in Control, the Holder will be able to
require the Company to purchase all or a portion of its Securities as described
under paragraph 7 herein.

      To convert a Security, a Holder must (1) complete and manually sign the
conversion notice below (or complete and manually sign a facsimile of such
notice) and deliver such notice to the Conversion Agent, (2) surrender the
Security to the Conversion Agent, (3) furnish appropriate endorsements and
transfer documents if required by the Conversion Agent, the Issuers or the
Trustee and (4) pay any transfer or similar tax, if required. The "Conversion
Date" as used herein refers to the date on which all of the foregoing
requirements have been satisfied.

      A Holder may convert a portion of a Security if the Initial Principal
Amount at Maturity of such portion is $1,000 or an integral multiple of $1,000.
No payment or adjustment will be made for dividends on the Common Stock except
as provided in the Indenture. On conversion of a Security, that portion of
accrued Contingent Additional Principal attributable to the period from the
Issue Date through the Conversion Date and (except as provided above) accrued
Contingent Cash Interest with respect to the converted Security shall not be
cancelled, extinguished or forfeited, but rather shall be deemed to be paid in
full to the Holder thereof through the delivery of the Cash Amount, together
with cash or Common Stock in respect of the Premium, in exchange for the
Security being converted pursuant to the terms hereof; and the fair market value
of such cash or Common Stock in respect of the Premium, shall be treated as
delivered to the extent thereof, first in exchange for Contingent Additional
Principal accrued through the Conversion Date and accrued Contingent Cash
Interest, and the Cash Amount shall be treated as delivered in exchange for the
Initial Principal Amount at Maturity of the Security being converted pursuant to
the provisions hereof.


                                      -9-
<PAGE>

      The Conversion Rate will be adjusted as provided in Article 10 of the
Indenture. However, no adjustment need be made if Securityholders may
participate in the transaction or in certain other cases. The Company from time
to time may voluntarily increase the Conversion Rate.

      In certain circumstances as provided for in the Indenture, when a Holder
surrenders a Security for conversion, the Conversion Agent may first offer the
Security to a financial institution chosen by the Issuers who will have the
option, but not the obligation (unless separately agreed to by it and the
Issuers at the time) to agree to exchange those Securities for the number of
shares of Common Stock that the Holder of those Securities would have been
otherwise entitled to receive upon conversion, plus cash for any fractional
shares."

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, the Company
      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 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


                                      -10-
<PAGE>

      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.

                            [Signature page follows]


                                      -11-
<PAGE>

         IN WITNESS WHEREOF, this Supplemental Indenture has been duly executed
by the Company, OCI 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/ Dennis E. Hewitt
                                            -----------------------------------
                                            Name:  Dennis E. Hewitt
                                            Title: Chief Executive Officer

                                        OMNICOM FINANCE INC.

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

                                        JPMORGAN CHASE BANK, as Trustee

                                        By: /s/ William G. Keenan
                                            -----------------------------------
                                            Name:  William G. Keenan
                                            Title: Vice President


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