SECURITIES AND EXCHANGE COMMISSION
                        Washington, D.C. 20549
                             SCHEDULE 13G
               Under the Securities Exchange Act of 1934
                          (Amendment No. 13)



                              VIACOM INC.
               ----------------------------------------
                           (Name of Issuer)

                 Class A Common Stock, $0.01 Par Value
               ----------------------------------------
                    (Title of Class of Securities)

                              925524 10 0
                ---------------------------------------
                            (CUSIP Number)


Check the following box if a fee is being paid with this  statement |_|.
(A fee is not required only if the filing person:  (1) has a previous
statement on file reporting  beneficial  ownership  of more  than  five
percent  of the class of securities  described  in Item 1;  and (2) has
filed  no  amendment subsequent thereto reporting  beneficial  ownership
of five percent or less of such class.) (See Rule 13d-7.)

*The  remainder of this cover page shall be filled out for a reporting
person's initial filing on this form with respect to the subject class of
securities, and for any  subsequent  amendment  containing  information
which  would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not
be deemed to be "filed" for the purpose of Section 18 of the  Securities
Exchange  Act of 1934 ("Act") or otherwise  subject to the liabilities
of that section of the Act but  shall be  subject  to all other  provisions
of the Act (however,  see the Notes).

                  (Continued on the following pages)

                              Page 1 of 6



CUSIP NO. 925524-10-0 (1) Name of Reporting Person S.S. or I.R.S. Identification No. of Above Person NAIRI, INC. ----------------------------------------------------------------- I.R.S. Identification No. 04-3446887 ----------------------------------------------------------------- (2) Check the Appropriate Box if a Member of Group See Instructions) / / (a) ------------------------------------------------------- / / (b) ------------------------------------------------------- (3) SEC Use Only ------------------------------------------------------- (4) Citizenship or Place of Organization Delaware ------------------------- - ----------- Number of (5) Sole Voting Power 93,658,828 Shares --------------- Beneficially (6) Shared Voting Power 0 Owned by --------------- Each (7) Sole Dispositive Power 93,658,828 Reporting --------------- Person With (8) Shared Dispositive Power 0 - ---------------------- --------------- (9) Aggregate Amount Beneficially Owned by Each Reporting Person 93,658,828 ----------------------------------------------------------------- (10) Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) --------------------------------------------- (11) Percent of Class Represented by Amount in Row (9) 67.7% ----------------------------------------------------------------- (12) Type of Reporting Person (See Instructions) CO -------------------- Page 2 of 6

CUSIP NO. 925524-10-0 (1) Name of Reporting Person S.S. or I.R.S. Identification No. of Above Person SUMNER M. REDSTONE ----------------------------------------------------------------- S.S. No. ----------------------------------------------------------------- (2) Check the Appropriate Box if a Member of Group See Instructions) / / (a) ------------------------------------------------------- / / (b) ------------------------------------------------------- (3) SEC Use Only ------------------------------------------------------- (4) Citizenship or Place of Organization United States ------------------------- - --------------------- Number of (5) Sole Voting Power 93,658,988* Shares --------------- Beneficially (6) Shared Voting Power 0 Owned by --------------- Each (7) Sole Dispositive Power 93,658,988* Reporting --------------- Person With (8) Shared Dispositive Power 0 - ---------------------- --------------- (9) Aggregate Amount Beneficially Owned by Each Reporting Person 93,658,988* ----------------------------------------------------------------- (10) Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) ------------------------------------------------------- (11) Percent of Class Represented by Amount in Row (9) 67.7% ----------------------------------------------------------------- (12) Type of Reporting Person (See Instructions) IN -------------------- - ------------------------ *Includes shares owned by NAIRI, Inc. Page 3 of 6

The Schedule 13G previously filed by the undersigned with respect to the Class A Common Stock, par value $0.01 per share (the "Class A Common Stock"), of Viacom Inc. (the "Company") is hereby amended as follows to reflect the transfer of shares of Class A Common Stock on December 29, 1999 from a parent company Reporting Person to its direct wholly owned subsidiary, which also becomes a Reporting Person on the Schedule: Item 1(b). Address of Issuer's Principal Executive Officers. -------------------------------------------------- Item 1(b) is amended as follows: 1515 Broadway New York, New York 10036 Item 2(a). Name of Person Filing. ----------------------- Item 2(a) is amended and restated as follows: This Statement is being filed jointly by NAIRI, Inc. ("NAIRI"), National Amusements, Inc. ("NAI") and Sumner M. Redstone. NAIRI is a wholly owned direct subsidiary of NAI. Mr. Redstone is the Chairman and President of NAIRI and the controlling stockholder, Chairman and Chief Executive Officer of NAI. Item 2(b). Address of Principal Business Office. ------------------------------------- Item 2(b) is amended and supplemented as follows: The principal business office of NAIRI is 200 Elm Street, Dedham, Massachusetts 02026. Item 2(c). Citizenship. ------------ Item 2(c) is amended and supplemented as follows: NAIRI is a Delaware corporation. Item 4. Ownership. ---------- Item 4 is amended and restated in its entirety as follows: (a) Amount Beneficially Owned: NAIRI beneficially owns 93,658,828 shares of Class A Common Stock; NAI beneficially owns 93,658,828 shares of Class A Common Stock; Sumner M. Redstone beneficially owns 93,658,988 shares of Class A Common Stock* (including the shares owned by NAIRI). (b) Percent of Class: 67.7% Page 4 of 6

(c) Number of shares as to which such person has: (i) sole power to vote or direct the vote: 93,658,828 shares of Class A Common Stock with respect to NAIRI and NAI; 93,658,988 shares of Class A Common Stock with respect to Mr. Redstone (including the shares owned by NAIRI); (ii) shared power to vote or direct the vote: None; (iii)sole power to dispose or direct the disposition of: 93,658,828 shares of Class A Common Stock with respect to NAIRI and NAI; 93,658,988 shares of Class A Common Stock with respect to Mr. Redstone (including the shares owned by NAIRI); (iv) shared power to dispose or to direct the disposition of: None. Page 5 of 6

Signatures - ---------- After reasonable inquiry and to the best of our knowledge and belief, we certify that the information set forth in this statement is true, complete and correct. Pursuant to Rule 13d-1(f)(1), we agree that this statement is filed on behalf of each of us. Date: January 7, 2000 /S/ SUMNER M. REDSTONE ----------------------------------- Sumner M. Redstone, Individually NAIRI, INC. By: /S/ SUMNER M. REDSTONE ------------------------------ Sumner M. Redstone, Chairman and President NATIONAL AMUSEMENTS, INC. By: /S/ SUMNER M. REDSTONE ------------------------------ Sumner M. Redstone, Chairman and Chief Executive Officer