SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549
                                 --------------

                                  SCHEDULE 13D

                 INFORMATION TO BE INCLUDED IN STATEMENTS FILED
                    PURSUANT TO RULE 13d-1(a) AND AMENDMENTS
                     THERETO FILED PURSUANT TO RULE 13d-2(a)

                             (Amendment No. 12)(1)

                                  GenCorp Inc.
 -------------------------------------------------------------------------------
                                (Name of Issuer)

                     Common Stock, Par Value $0.10 Per Share
 -------------------------------------------------------------------------------
                         (Title of class of securities)

                                    368682100
 -------------------------------------------------------------------------------
                                 (CUSIP number)

                              STEVEN WOLOSKY, ESQ.
                 OLSHAN GRUNDMAN FROME ROSENZWEIG & WOLOSKY LLP
                                Park Avenue Tower
                               65 East 55th Street
                            New York, New York 10022
                                 (212) 451-2300
 -------------------------------------------------------------------------------
                  (Name, address and telephone number of person
                authorized to receive notices and communications)

                                 August 1, 2007
 -------------------------------------------------------------------------------
             (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 |_|.

      Note.  Schedules filed in paper format shall include a signed original and
five copies of the schedule,  including  all exhibits.  SEE Rule 13d-7 for other
parties to whom copies are to be sent.

                         (Continued on following pages)

                               (Page 1 of 7 Pages)


--------
(1)   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 disclosures provided in a prior cover page.

      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 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).



----------------------                                     ---------------------
Cusip No. 368682100                   13D                     Page 2 of 7 Pages
----------------------                                     ---------------------


================================================================================
     1         NAME OF REPORTING PERSONS
               I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

                    STEEL PARTNERS II, L.P.
--------------------------------------------------------------------------------
     2         CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*         (a) / /
                                                                         (b) / /
--------------------------------------------------------------------------------
     3         SEC USE ONLY

--------------------------------------------------------------------------------
     4         SOURCE OF FUNDS*

                    WC
--------------------------------------------------------------------------------
     5         CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
               PURSUANT TO ITEM 2(d) OR 2(e)                                 / /
--------------------------------------------------------------------------------
     6         CITIZENSHIP OR PLACE OF ORGANIZATION

                    DELAWARE
--------------------------------------------------------------------------------
 NUMBER OF         7     SOLE VOTING POWER
   SHARES
BENEFICIALLY                  7,226,354
  OWNED BY     -----------------------------------------------------------------
    EACH           8     SHARED VOTING POWER
 REPORTING
PERSON WITH                   0
               -----------------------------------------------------------------
                   9     SOLE DISPOSITIVE POWER

                              7,226,354
               -----------------------------------------------------------------
                  10     SHARED DISPOSITIVE POWER

                              0
--------------------------------------------------------------------------------
    11         AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING
               PERSON

                    7,226,354
--------------------------------------------------------------------------------
    12         CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
               CERTAIN SHARES*                                               / /
--------------------------------------------------------------------------------
    13         PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

                    12.8%
--------------------------------------------------------------------------------
    14         TYPE OF REPORTING PERSON*

                    PN
================================================================================

                      *SEE INSTRUCTIONS BEFORE FILLING OUT!



----------------------                                     ---------------------
Cusip No. 368682100                   13D                     Page 3 of 7 Pages
----------------------                                     ---------------------


================================================================================
     1         NAME OF REPORTING PERSONS
               I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

                    STEEL PARTNERS, L.L.C.
--------------------------------------------------------------------------------
     2         CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*         (a) / /
                                                                         (b) / /
--------------------------------------------------------------------------------
     3         SEC USE ONLY

--------------------------------------------------------------------------------
     4         SOURCE OF FUNDS*

                    OO
--------------------------------------------------------------------------------
     5         CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
               PURSUANT TO ITEM 2(d) OR 2(e)                                 / /
--------------------------------------------------------------------------------
     6         CITIZENSHIP OR PLACE OF ORGANIZATION

                    DELAWARE
--------------------------------------------------------------------------------
 NUMBER OF         7     SOLE VOTING POWER
   SHARES
BENEFICIALLY                  7,226,354
  OWNED BY     -----------------------------------------------------------------
    EACH           8     SHARED VOTING POWER
 REPORTING
PERSON WITH                   0
               -----------------------------------------------------------------
                   9     SOLE DISPOSITIVE POWER

                              7,226,354
               -----------------------------------------------------------------
                  10     SHARED DISPOSITIVE POWER

                              0
--------------------------------------------------------------------------------
    11         AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING
               PERSON

                    7,226,354
--------------------------------------------------------------------------------
    12         CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
               CERTAIN SHARES*                                               / /
--------------------------------------------------------------------------------
    13         PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

                    12.8%
--------------------------------------------------------------------------------
    14         TYPE OF REPORTING PERSON*

                    OO
================================================================================

                      *SEE INSTRUCTIONS BEFORE FILLING OUT!



----------------------                                     ---------------------
Cusip No. 368682100                   13D                     Page 4 of 7 Pages
----------------------                                     ---------------------


================================================================================
     1         NAME OF REPORTING PERSONS
               I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

                    WARREN G. LICHTENSTEIN
--------------------------------------------------------------------------------
     2         CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*         (a) / /
                                                                         (b) / /
--------------------------------------------------------------------------------
     3         SEC USE ONLY

--------------------------------------------------------------------------------
     4         SOURCE OF FUNDS*

                    OO
--------------------------------------------------------------------------------
     5         CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
               PURSUANT TO ITEM 2(d) OR 2(e)                                 / /
--------------------------------------------------------------------------------
     6         CITIZENSHIP OR PLACE OF ORGANIZATION

                    USA
--------------------------------------------------------------------------------
 NUMBER OF         7     SOLE VOTING POWER
   SHARES
BENEFICIALLY                  7,226,354
  OWNED BY     -----------------------------------------------------------------
    EACH           8     SHARED VOTING POWER
 REPORTING
PERSON WITH                   0
               -----------------------------------------------------------------
                   9     SOLE DISPOSITIVE POWER

                              7,226,354
               -----------------------------------------------------------------
                  10     SHARED DISPOSITIVE POWER

                              0
--------------------------------------------------------------------------------
    11         AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING
               PERSON

                    7,226,354
--------------------------------------------------------------------------------
    12         CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
               CERTAIN SHARES*                                               / /
--------------------------------------------------------------------------------
    13         PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

                    12.8%
--------------------------------------------------------------------------------
    14         TYPE OF REPORTING PERSON*

                    IN
================================================================================

                      *SEE INSTRUCTIONS BEFORE FILLING OUT!



----------------------                                     ---------------------
Cusip No. 368682100                   13D                     Page 5 of 7 Pages
----------------------                                     ---------------------

            The following  constitutes  Amendment No. 12 ("Amendment  No. 12")
to the Schedule 13D filed by the  undersigned.  This  Amendment  No. 12 amends
the Schedule 13D as specifically set forth.

      Item 3 is hereby amended and restated to read as follows:

            The aggregate  purchase price of the 7,226,354 Shares owned by Steel
Partners II is $85,484,724.  The Shares owned by Steel Partners II were acquired
with partnership funds.

      Item 5(a) is hereby amended and restated to read as follows:

            (a)The aggregate  percentage of Shares reported owned by each person
named herein is based upon  56,300,000  Shares  outstanding,  which is the total
number of Shares  outstanding  as of June 25, 2007 as  reported in the  Issuer's
Quarterly Report on Form 10-Q, filed with the Securities and Exchange Commission
on June 27, 2007.

            As of the close of  business  on August 2, 2007,  Steel  Partners II
beneficially  owned 7,226,354 Shares,  constituting  approximately  12.8% of the
Shares  outstanding.  As the general  partner of Steel Partners II, Partners LLC
may be deemed to beneficially  own the 7,226,354  Shares owned by Steel Partners
II,  constituting  approximately  12.8% of the Shares  outstanding.  As the sole
executive  officer and  managing  member of Partners  LLC,  which in turn is the
general  partner of Steel Partners II, Warren G.  Lichtenstein  may be deemed to
beneficially own the 7,226,354  Shares owned by Steel Partners II,  constituting
approximately 12.8% of the Shares outstanding.  Mr. Lichtenstein has sole voting
and  dispositive  power with  respect  to the  7,226,354  Shares  owned by Steel
Partners II by virtue of his authority to vote and dispose of such Shares.

      Item 5(c) is hereby amended to add the following:

            (c) Schedule A annexed hereto lists all  transactions  in the Shares
by the  Reporting  Persons  since the filing of Amendment No. 11 to the Schedule
13D. All of such transactions were effected in the open market.



----------------------                                     ---------------------
Cusip No. 368682100                   13D                     Page 6 of 7 Pages
----------------------                                     ---------------------


                                   SIGNATURES

      After reasonable inquiry and to the best of his knowledge and belief, each
of the undersigned certifies that the information set forth in this statement is
true, complete and correct.

Dated: August 3, 2007               STEEL PARTNERS II, L.P.

                                    By:  Steel Partners, L.L.C.,
                                         General Partner

                                    By: /s/ Lauren Isenman
                                       -----------------------------------------
                                       Lauren Isenman
                                       As Attorney in Fact for Warren G.
                                       Lichtenstein, Managing Member


                                    STEEL PARTNERS, L.L.C.

                                    By: /s/ Lauren Isenman
                                       -----------------------------------------
                                       Lauren Isenman
                                       as Attorney In Fact for Warren G.
                                       Lichtenstein, Managing Member


                                    /s/ Lauren Isenman
                                    --------------------------------------------
                                    LAUREN ISENMAN
                                    as Attorney In Fact for Warren G.
                                    Lichtenstein, Individually



----------------------                                     ---------------------
Cusip No. 368682100                   13D                     Page 7 of 7 Pages
----------------------                                     ---------------------


                                   SCHEDULE A

     TRANSACTIONS IN THE SHARES SINCE THE FILING OF AMENDMENT NO. 11 TO THE
                                  SCHEDULE 13D

  Shares of Common Stock           Price Per                  Date of
        Purchased*                 Share($)                  Purchase
        ----------                 --------                  --------

                             STEEL PARTNERS II, L.P.
                             -----------------------


        250,000                     12.4605                  07/27/07

        250,000                     11.8647                  07/30/07

         31,300                     11.8890                  07/31/07

        250,000                     11.9076                  08/01/07

        250,000                     12.0305                  08/02/07


                             STEEL PARTNERS, L.L.C.
                             ----------------------
                                      None


                             WARREN G. LICHTENSTEIN
                             ----------------------
                                      None


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

*  The  transactions  reported in this Schedule 13D were effected  pursuant to a
   Rule 10b5-1 Purchase Trading Plan.