SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13D

                    Under the Securities Exchange Act of 1934
                                (Amendment No. 2)

                         Cablevision Systems Corporation
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                                (Name of Issuer)
                 Class A Common Stock, Par Value $.01 Per Share
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                         (Title of Class of Securities)
                                   12686C 10 9
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                                 (CUSIP Number)
                                Marilyn J. Wasser
                       Vice President - Law and Secretary
                                   AT&T Corp.
                             295 North Maple Avenue
                            Basking Ridge, NJ 07920
                                 (908) 221-2000
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            (Name, Address and Telephone Number of Person Authorized
                     to Receive Notices and Communications)
                                 April 5, 2001
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            (Date of Event which Requires Filing of this Statement)

If the filing person has previously  filed a statement on Schedule 13G to report
the  acquisition  that is the subject of this  Schedule  13D, and is filing this
schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box
/__/.

The information required on 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).


                                  SCHEDULE 13D
---------------------                                 --------------------------
CUSIP No. 12686C 10 9                                 Page 2 of ___ Pages
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     1    NAME OF REPORTING PERSON
          S.S. OR I.R.S. IDENTIFICATION NO.
            OF ABOVE PERSON
               AT&T Corp.
               I.R.S. Identification No. 13-4924710
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     2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) /__/
                                                           (b) /__/
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     3    SEC USE ONLY
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     4    SOURCE OF FUNDS WC, OO
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     5    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
            TO ITEMS 2(d) or 2(e)
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     6    CITIZENSHIP OR PLACE OF ORGANIZATION New York
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               7    SOLE VOTING POWER 48,942,172
  NUMBER OF   ------------------------------------------------------------------
   SHARES      8    SHARED VOTING POWER BENEFICIALLY
BENEFICIALLY          -0-
  OWNED BY    ------------------------------------------------------------------
    EACH       9    SOLE DISPOSITIVE POWER
 REPORTING            48,942,172*
   PERSON     ------------------------------------------------------------------
    WITH      10    SHARED DISPOSITIVE POWER
                      -0-
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    11    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
            48,942,172
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    12    CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
            CERTAIN SHARES                                            /__/
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    13    PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
            45.2%**
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    14    TYPE OF REPORTING PERSON
            C0

* Subject to the Stockholders Agreement (See Item 6 hereof).

** Each share of the  Issuer's  Class B Common Stock is entitled to 10 votes per
share and each share of Class A Common  Stock is entitled to one vote per share.
Holders  of Class B Common  Stock and Class A Common  Stock vote  together  as a
single class, except for the election of directors. With respect to the election
of directors and subject to certain conditions,  holders of Class A Common Stock
vote as a separate  class and are  entitled to elect 25% of the total  number of
directors  constituting the whole board. For all other issues,  when the classes
of stock are aggregated,  the Reporting Person may be deemed to beneficially own
voting equity securities of the Issuer  representing  approximately  9.1% of the
voting power of the Issuer (See Items 1 and 5).


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CUSIP No. 12686C 10 9                                 Page 3 of ___ Pages
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Item 1.   Security and Issuer.

          This  Amendment  2 relates to the Class A Common  Stock,  par value of
$.01 per share (the "Common  Stock"),  of  Cablevision  Systems  Corporation,  a
Delaware corporation (the "Issuer"),  One Media Crossways,  Woodbury,  NY 11797.
This Amendment  amends the Schedule 13D Statement  (the "Schedule  13D") of AT&T
Corp., a New York corporation ("AT&T") relating to the Issuer filed on March 19,
1999,  as amended by Amendment 1 filed on December 15, 2000.  Capitalized  terms
used herein and not defined have the  meanings  ascribed to them in the Schedule
13D as previously amended.

Item 4.   Purpose of Transaction.

          Item 4 is hereby amended by replacing the last paragraph  thereof with
the following:

          AT&T is also  evaluating a direct or indirect  disposition of all or a
          portion of its shares in the Issuer  even if not  required in order to
          comply  with  the  FCC  MediaOne   Order.   In  connection  with  such
          evaluation,  AT&T delivered a demand request to the Issuer on April 5,
          2001 pursuant to Annex A to the Stockholders  Agreement to register 30
          million shares of Common Stock. Any disposition  would be dependent on
          market  conditions,  AT&T's own business  opportunities  and liquidity
          goals and other  factors  as well as the other  factors  listed in the
          preceding   paragraphs   and  there  can  be  no  assurance  that  any
          disposition  will  occur  or as to  the  timing,  terms  or  structure
          thereof.

                              -------------------


                                   SIGNATURE

     After  reasonable  inquiry and to the best of my  knowledge  and belief,  I
certify that the information  set forth in this statement is true,  complete and
correct.


Dated: April 9, 2001


                                        AT&T CORP.


                                        By:  /s/  Robert S. Feit
                                             -------------------
                                        Name:     Robert S. Feit
                                        Title:    Authorized Signatory