<PAGE>

                                                                     EXHIBIT 4.2


            UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE
OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION ("DTC"), TO THE COMPANY
(AS DEFINED BELOW) OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR
PAYMENT, AND ANY CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR
SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY
PAYMENT IS MADE TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN
AUTHORIZED REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR
VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED
OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

            UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR SECURITIES
IN DEFINITIVE REGISTERED FORM IN ACCORDANCE WITH THE PROVISIONS OF THE INDENTURE
(AS DEFINED BELOW) APPLICABLE TO SUCH EXCHANGE, THIS CERTIFICATE MAY NOT BE
TRANSFERRED EXCEPT AS A WHOLE BY DTC TO A NOMINEE OF DTC OR BY A NOMINEE OF DTC
TO DTC OR ANOTHER NOMINEE OF DTC OR BY DTC OR ANY SUCH NOMINEE TO A SUCCESSOR
DEPOSITORY OR A NOMINEE OF SUCH SUCCESSOR DEPOSITORY.

                                   VIACOM INC.

                        7.875% Senior Debentures due 2030

                   Unconditionally guaranteed as to payment of
                          principal of and interest by
                            VIACOM INTERNATIONAL INC.
                   (a wholly owned subsidiary of Viacom Inc.)

No. [_]                                                          $[____________]

                                                             CUSIP:  925524 AH 3
                                                                 CINS:  11553508
                                                           ISIN:  US925524 AH 30

            Viacom Inc., a Delaware corporation (herein called the "Company",
which term includes any successor Person under the Indenture hereinafter
referred to), for value received, hereby promises to pay to Cede & Co., or
registered assigns, the principal sum of $[_________] on July 30, 2030, at the
office or agency of the Company referred to below, and to pay interest thereon
on January 30, 2001 and semi-annually thereafter, on January 30 and July 30 in
each year, from August 1, 2000, or from the most recent Interest Payment Date to
which interest has been paid or duly provided for, at the rate of 7.875% per
annum, until the principal hereof is paid or duly provided for. The interest so
payable, and punctually paid or duly provided for, on any Interest Payment Date
will, as provided in such Indenture, be paid, in immediately available funds, to
the Person in whose name this

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                                       2


Security (or one or more Predecessor Securities) is registered at the close of
business on the Regular Record Date for such interest, which shall be the
January 15 or July 15, as the case may be, next preceding such Interest Payment
Date. Any such interest not so punctually paid or duly provided for shall
forthwith cease to be payable to the Holder on such Regular Record Date, and
such defaulted interest, may be paid to the Person in whose name this Security
(or one or more Predecessor Securities) is registered at the close of business
on a Special Record Date for the payment of such Defaulted Interest to be fixed
by the Trustee, notice whereof shall be given to Holders of Securities not less
than 10 days prior to such Special Record Date, or may be paid at any time in
any other lawful manner not inconsistent with the requirements of any securities
exchange on which the Securities may be listed, and upon such notice as may be
required by such exchange, all as more fully provided in said Indenture. Payment
of the principal of and interest on this Security will be made at the Corporate
Trust Office of the Trustee or such other office or agency of the Company as may
be designated for such purpose, in such coin or currency of the United States of
America as at the time of payment is legal tender for payment of public and
private debts; PROVIDED HOWEVER, that each installment of interest and principal
on this Security may at the Company's option be paid in immediately available
funds by transfer to an account maintained by the payee located in the United
States.

            This Security is one of a duly authorized issue of securities of the
Company (herein called the "Securities"), unlimited in aggregate principal
amount, issued and to be issued in one or more series under an indenture dated
as of May 15, 1995 among the Company, Viacom International Inc., as guarantor
(the "Guarantor") and Citibank, N.A., as successor to State Street Bank and
Trust Company and The First National Bank of Boston, trustee (herein called the
"Trustee", which term includes any successor trustee under the Indenture), as
supplemented by the First Supplemental Indenture dated as of May 24, 1995 among
the Company, the Guarantor and the trustee party thereto, as supplemented and
amended by the Second Supplemental Indenture and Amendment No. 1 dated as of
December 15, 1995 among the Company, the Guarantor and the trustee party
thereto, as supplemented by the Third Supplemental Indenture dated as of July
22, 1996, among the Company, the Guarantor and the trustee party thereto and as
further supplemented by the Fourth Supplemental Indenture dated as of August 1,
2000 among the Company, the Guarantor and the Trustee (as so supplemented and
amended, the "Indenture"), to which Indenture and all indentures supplemental
thereto reference is hereby made for a statement of the respective rights,
limitations of rights, duties, obligations and immunities thereunder of the
Company, the Trustee and the Holders of the Securities, and of the terms upon
which the Securities are, and are to be, authenticated and delivered. This
Security is one of a series designated as 7.875% Senior Debentures due 2030,
initially limited in aggregate principal amount to $500,000,000. This Security
is a global Security representing $[____________] of the Securities.

            If an Event of Default with respect to Securities of this series
shall occur and be continuing, the principal of the Securities of this series
may be declared due and payable in the manner and with the effect provided in
the Indenture.

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                                       3


            The Securities of this series are not subject to any sinking fund
and are subject to redemption prior to maturity as set forth below.

            In the event that as a result of any change in, or amendments to,
any laws (or any regulations or rulings promulgated thereunder) of the United
States (or any political subdivision or taxing authority thereof or therein) or
any change in, or amendments to, an official position regarding the application
of such laws, regulations or rulings, which change or amendment is announced or
becomes effective thereunder after July 25, 2000, the Company has become or,
based upon a written opinion of independent counsel selected by the Company,
will become obligated to pay, with respect to this series of Securities, any
Additional Amounts, the Company may redeem all, but not less than all, the
Securities of such series at any time at 100% of the principal amount thereof,
together with accrued interest thereon, if any, to the Redemption Date (subject
to the rights of holders of record on the relevant Regular Record Date that is
prior to the Redemption Date to receive interest on the relevant Interest
Payment Date).

            The Securities of this series will be redeemable at any time, at the
option of the Company, in whole or from time to time in part, upon not less than
30 nor more than 60 days' prior notice, on any date prior to their maturity at a
Redemption Price equal to the sum of 100% of the principal amount thereof and
the Make-Whole Amount and any accrued and unpaid interest, to the Redemption
Date (subject to the rights of holders of record on the relevant Regular Record
Date that is on or prior to the Redemption Date to receive interest due on the
relevant Interest Payment Date).

            In the case of any partial redemption, selection of the Securities
of this series for redemption will be made by the Trustee in compliance with the
requirements of the principal national securities exchange, if any, on which the
Securities of this series are listed or, if the Securities of this series are
not listed on a national securities exchange, by lot or by such other method as
the Trustee in its sole discretion shall deem to be fair and appropriate;
PROVIDED that no Securities of this series of $1,000 in principal amount or less
shall be redeemed in part. If any Note is to be redeemed in part only, the
notice of redemption relating to such Security shall state the portion of the
principal amount thereof to be redeemed. A new Security in principal amount
equal to the unredeemed portion thereof will be issued in the name of the Holder
thereof upon cancellation of the original Security.

            The Indenture contains provisions for defeasance at any time of (a)
the entire indebtedness of the Company on this Security and (b) certain
restrictive covenants and the related Defaults and Events of Default, upon
compliance by the Company with certain conditions set forth therein, which
provisions apply to this Security.

            The Indenture permits, with certain exceptions as therein provided,
the amendment thereof and the modification of the rights and obligations of the
Company and the rights of the Holders of the

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                                       4


Securities of each series to be affected under the Indenture at any time by the
Company, the Guarantor and the Trustee with the consent of the Holders of not
less than a majority in principal amount of the Outstanding Securities of each
series affected thereby. The Indenture also contains provisions permitting the
Holders of not less than specified percentages in aggregate principal amount of
the Outstanding Securities of each series, on behalf of the Holders of all the
Securities of such series, to waive compliance by the Company and the Guarantor
with certain provisions of the Indenture and certain past defaults under the
Indenture and their consequences. Any such consent or waiver by or on behalf of
the Holder of this Security shall be conclusive and binding upon such Holder and
upon all future Holders of this Security and of any Security issued upon the
registration of transfer hereof or in exchange herefor or in lieu hereof whether
or not notation of such consent or waiver is made upon this Security.

            As set forth in, and subject to, the provisions of the Indenture, no
Holder of any Security of this series will have any right to institute any
proceeding with respect to the Indenture or for any remedy thereunder, unless
such Holder shall have previously given to the Trustee written notice of a
continuing Event of Default with respect to this series, the Holders of not less
than 25% in principal amount of the Outstanding Securities of this series shall
have made written request, and offered reasonable indemnity, to the Trustee to
institute such proceeding as trustee, and the Trustee shall not have received
from the Holders of a majority in principal amount of the Outstanding Securities
of this series a direction inconsistent with such request and shall have failed
to institute such proceeding within 60 days; provided however, that such
limitations do not apply to a suit instituted by the Holder hereof for the
enforcement of payment of the principal of or interest on this Security on or
after the respective due dates expressed herein.

            No reference herein to the Indenture and no provision of this
Security or of the Indenture shall alter or impair the obligation of the
Company, which is absolute and unconditional, to pay the principal of and
interest on this Security at the times, place, and rate, and in the coin or
currency, herein prescribed.

            As provided in the Indenture and subject to certain limitations
therein set forth, the transfer of this Security is registerable on the Security
Register of the Company, upon surrender of this Security for registration of
transfer at the office or agency of the Company maintained for such purpose in
New York, New York or at such other office or agency as the Company may
designate, duly endorsed by, or accompanied by a written instrument of transfer
in form satisfactory to the Company and the Security Registrar duly executed by,
the Holder hereof or his attorney duly authorized in writing, and thereupon one
or more new Securities of this series of authorized denominations and for the
same aggregate principal amount, will be issued to the designated transferee or
transferees.

            The Securities of this series are issuable only in registered form
without coupons in denominations of $1,000 and any integral multiple thereof. As
provided in the Indenture and subject to certain limitations therein set forth,
the Securities of this series are exchangeable for a like aggregate principal
amount of Securities of this series and of a different authorized denomination,
as requested by the Holder surrendering the same.

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                                       5


            No service charge shall be made for any registration of transfer or
exchange of Securities, but the Company may require payment of a sum sufficient
to cover any tax or other governmental charge payable in connection therewith.

            Prior to the time of due presentment of this Security for
registration of transfer, the Company, the Guarantor, the Trustee and any agent
of the Company, the Guarantor or the Trustee may treat the Person in whose name
this Security is registered as the absolute owner hereof for all purposes,
whether or not this Security be overdue, and none of the Company, the Guarantor,
the Trustee or any agent of the Company, the Guarantor or the Trustee shall be
affected by notice to the contrary.

            If at any time, a Depositary is at any time unwilling or unable to
continue as Depositary and a successor Depositary is not appointed by the
Company within 90 days, then the Company will execute and the Trustee will
authenticate and deliver Securities in definitive registered form, in authorized
denominations, and in an aggregate principal amount equal to the principal
amount of this Security in exchange for this Security. Such Securities in
definitive registered form shall be registered in such names and issued in such
authorized denominations as the Depositary, pursuant to instructions from its
direct or indirect participants or otherwise, shall instruct the Trustee. The
Trustee shall deliver such Securities to the Persons in whose names such
Securities are so registered.

            Unless the certificate of authentication hereon has been duly
executed by or on behalf of Citibank, N.A., the Trustee under the Indenture, or
its successor thereunder, by the manual signature of one of its authorized
officers, this Security shall not be entitled to any benefit under the
Indenture, or be valid or obligatory for any purpose.

            This Security shall be governed by, and construed in accordance
with, the laws of the State of New York.


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                                       6


         IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed.

      Dated: [____________]                     VIACOM INC.,
                                                as Issuer

                                                By______________________________

Attest:


__________________________
Authorized Signature


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                                       7


                     TRUSTEE'S CERTIFICATE OF AUTHENTICATION


            This is one of the Securities of a series referred to in the
within-mentioned Indenture.

                                          CITIBANK, N.A., as Trustee


                                          By____________________________________
                                                Authorized Signatory
Dated: [_____________]


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                                       8


                     GUARANTEE OF VIACOM INTERNATIONAL INC.


            FOR VALUE RECEIVED, VIACOM INTERNATIONAL INC., a corporation duly
organized and existing under the laws of the State of Delaware (herein called
the "Guarantor", which term includes any successor corporation under the
Indenture referred to in the Security upon which this Guarantee is endorsed),
hereby fully and unconditionally guarantees to the holder of the Security upon
which this Guarantee is endorsed the due and punctual payment of the principal
of and interest (including, in case of default, interest on principal and, to
the extent permitted by applicable law, on overdue interest), if any, on this
Security, when and as the same shall become due and payable, whether at Stated
Maturity, upon redemption, upon declaration of acceleration or otherwise,
according to the terms thereof and of the Indenture referred to therein. In case
of the failure of Viacom Inc. or any successor thereto (herein called the
"Company") punctually to pay any such principal or interest, the Guarantor
hereby agrees to cause any such payment to be made punctually when and as the
same shall become due and payable, whether at Stated Maturity, upon redemption,
upon declaration of acceleration or otherwise, as if such payment were made by
the Company.

            The Guarantor hereby agrees that its obligations hereunder shall be
as if it were principal debtor and not merely surety, and shall be absolute and
unconditional, irrespective of the identity of the Company, the validity,
regularity or enforceability of this Security or said Indenture, the absence of
any action to enforce the same, any waiver or consent by the Holder of this
Security with respect to any provisions thereof, the recovery of any judgment
against the Company or any action to enforce the same, or any other circumstance
which might otherwise constitute a legal or equitable discharge or defense of a
guarantor. The Guarantor hereby waives diligence, presentment, demand of
payment, filing of claims with a court in the event of insolvency or bankruptcy
of the Company, any right to require a proceeding first against the Company,
protest, notice and all demands whatsoever and covenants that this Guarantee
will not be discharged except by complete performance of the obligations
contained in this Security and in this Guarantee.

            The Guarantor shall be subrogated to all rights of the Holder of
this Security against the Company in respect of any amounts paid by the
Guarantor pursuant to the provisions of this Guarantee or the Indenture referred
to in this Security; PROVIDED, HOWEVER, that the Guarantor shall not be entitled
to enforce or to receive any payment arising out of, or based upon, such right
of subrogation until the principal of and interest on all Securities of the
series of which the Security upon which this Guarantee is endorsed constitutes a
part shall have been indefeasibly paid in full.

            The Indenture provides that in the event that this Guarantee would
constitute or result in a fraudulent transfer or conveyance for purposes of, or
result in a violation of, any United States federal, or applicable United States
state, fraudulent transfer or conveyance or similar law, then the liability of
the Guarantor hereunder shall be reduced to the extent necessary to eliminate
such fraudulent transfer or conveyance or violation under the applicable
fraudulent transfer or conveyance or similar law.

<PAGE>
                                       9


            If the Trustee or the Holder of the Security upon which this
Guarantee is endorsed is required by any court or otherwise to return to the
Company or the Guarantor, or any custodian, receiver, liquidator, assignee,
trustee, sequestrator or other similar official acting in relation to the
Company or the Guarantor, any amount paid to the Trustee or such Holder in
respect of the Security upon which this Guarantee is endorsed, this Guarantee,
to the extent theretofore discharged, shall be reinstated in full force and
effect. The Guarantor further agrees, to the fullest extent that it may lawfully
do so, that, as between the Guarantor, on the one hand, and the Holders and the
Trustee, on the other hand, the maturity of the obligations guaranteed hereby
may be accelerated as provided in Article Five of the Indenture for the purposes
of this Guarantee, notwithstanding any stay, injunction or other prohibition
extant under any applicable bankruptcy law preventing such acceleration in
respect of the obligations guaranteed hereby.

            This Guarantee shall be governed by, and construed in accordance
with, the laws of the State of New York.

            Subject to the next following paragraph, the Guarantor hereby
certifies and warrants that all acts, conditions and things required to be done
and performed and to have happened precedent to the creation and issuance of
this Guarantee and to constitute the same valid obligation of the Guarantor have
been done and performed and have happened in due compliance with all applicable
laws.

            This Guarantee shall not be valid or become obligatory for any
purpose until the certificate of authentication on the Security upon which this
Guarantee is endorsed has been signed by the Trustee under the Indenture
referred to in this Security.



<PAGE>



            IN WITNESS WHEREOF, the Guarantor has caused this Guarantee to be
signed by its Chairman of the Board, or its Vice Chairman of the Board, or its
President, or one of its Executive Vice Presidents or Vice Presidents, or by its
Treasurer or one of its Assistant Treasurers and attested by its Secretary or
one of its Assistant Secretaries, manually or in facsimile.


Dated: [_____________]                    VIACOM INTERNATIONAL INC.


                                          By____________________________________

ATTEST:__________________