SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549

                                  SCHEDULE 13G

                    Under the Securities Exchange Act of 1934


                          AK Steel Holding Corporation
                                (Name of Issuer)


                          Common Stock, $0.01 par value
                         (Title of Class of Securities)


                                    001547108
                                 (CUSIP Number)


                                 March 31, 2006
             (Date of Event Which Requires Filing of this Statement)

Check the following box to designate the rule pursuant to which the Schedule is
filed:

  [     ]   Rule 13d-1(b)
  [  X  ]   Rule 13d-1(c)
  [     ]   Rule 13d-1(d)


*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).




CUSIP NO. 001547108

   1.    NAMES OF REPORTING PERSONS. I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS
         (ENTITIES ONLY)
         D. E. Shaw & Co., L.P.
         13-3695715

   2.    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
         (a)         [ ]
         (b)         [ ]

   3.    SEC USE ONLY

   4.    CITIZENSHIP OR PLACE OF ORGANIZATION
         Delaware

NUMBER OF                 5.    SOLE VOTING POWER
SHARES
BENEFICIALLY
OWNED BY                        -0-
EACH
REPORTING
PERSON WITH
                          6.    SHARED VOTING POWER
                                5,950,800

                          7.    SOLE DISPOSITIVE POWER
                                -0-

                          8.    SHARED DISPOSITIVE POWER
                                5,950,800

   9.    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
         5,950,800

   10.   CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE
         INSTRUCTIONS)  [     ]

   11.   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
         5.4%

   12.   TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
         IA, PN



CUSIP NO. 001547108

      1.   NAMES OF REPORTING PERSONS. I.R.S. IDENTIFICATION NOS. OF ABOVE
           PERSONS (ENTITIES ONLY)
           David E. Shaw

      2.   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
           (a)         [ ]
           (b)         [ ]

      3.   SEC USE ONLY

      4.   CITIZENSHIP OR PLACE OF ORGANIZATION
           United States

NUMBER OF                    5.   SOLE VOTING POWER
SHARES
BENEFICIALLY
OWNED BY                          -0-
EACH
REPORTING
PERSON WITH
                             6.   SHARED VOTING POWER
                                  5,950,800

                             7.   SOLE DISPOSITIVE POWER
                                  -0-

                             8.   SHARED DISPOSITIVE POWER
                                  5,950,800

      9.   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
           5,950,800

      10. CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE
          INSTRUCTIONS) [ ]

      11.  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
           5.4%

      12.  TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
           IN



ITEM 1.
     (a)   NAME OF ISSUER
           AK Steel Holding Corporation



     (b)   ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES
           703 Curtis Street
           Middletown, OH 45043


ITEM 2.
     (a)   NAME OF PERSON FILING
           D. E. Shaw & Co., L.P.
           David E. Shaw



     (b)   ADDRESS OF PRINCIPAL BUSINESS OFFICE OR, IF NONE, RESIDENCE
           The business address for each reporting person is:
           120 W. 45th Street, Tower 45, 39th Floor
           New York, NY 10036



     (c)   CITIZENSHIP
           D. E. Shaw & Co., L.P. is a limited partnership organized under the
           laws of the state of Delaware.
           David E. Shaw is a citizen of the United States of America.



     (d)   TITLE OF CLASS OF SECURITIES
           Common Stock, $0.01 par value



     (e)   CUSIP NUMBER
           001547108



ITEM 3. IF THIS STATEMENT IS FILED PURSUANT TO RULE 13d-1(b) OR 13d-2(b) OR (c),
CHECK WHETHER THE PERSON FILING IS A:

Not applicable

ITEM 4.        OWNERSHIP

As of April 5, 2006:

(a) Amount beneficially owned:

D. E. Shaw & Co., L.P.:    5,950,800 shares
                           This is composed of (i) 2,261,000 shares in the name
                           of D. E. Shaw Oculus Portfolios, L.L.C., (ii)
                           3,677,500 shares in the name of D. E. Shaw Valence
                           Portfolios, L.L.C., and (iii) 12,300 shares that
                           D. E. Shaw Valence, L.L.C. has the right to acquire
                           through the exercise of listed call options.

David E. Shaw:             5,950,800 shares
                           This is composed of (i) 2,261,000 shares in the name
                           of D. E. Shaw Oculus Portfolios, L.L.C., (ii)
                           3,677,500 shares in the name of D. E. Shaw Valence
                           Portfolios, L.L.C., and (iii) 12,300 shares that
                           D. E. Shaw Valence, L.L.C. has the right to acquire
                           through the exercise of listed call options.

(b) Percent of class:
    D. E. Shaw & Co., L.P.: 5.4%
    David E. Shaw:          5.4%


(c) Number of shares to which the person has:
   (i) Sole power to vote or to direct the vote:
       D. E. Shaw & Co., L.P.:      -0- shares
       David E. Shaw:              -0- shares

   (ii) Shared power to vote or to direct the vote:


         D. E. Shaw & Co., L.P.:     5,950,800 shares
         David E. Shaw:              5,950,800 shares


   (iii) Sole power to dispose or to direct the disposition of:
         D. E. Shaw & Co., L.P.:     -0- shares
         David E. Shaw:              -0- shares


   (iv)  Shared power to dispose or to direct the disposition of:
         D. E. Shaw & Co., L.P.:     5,950,800 shares
         David E. Shaw:              5,950,800 shares


David E. Shaw does not own any shares directly. By virtue of David E. Shaw's
position as President and sole shareholder of D. E. Shaw & Co., Inc., which is
the general partner of D. E. Shaw & Co., L.P., which in turn is the investment
adviser of D. E. Shaw Oculus Portfolios, L.L.C., the managing member and
investment adviser of D. E. Shaw Valence Portfolios, L.L.C., and the managing
member of D. E. Shaw Valence, L.L.C., and by virtue of David E. Shaw's position
as President and sole shareholder of D. E. Shaw & Co. II, Inc., which is the
managing member of D. E. Shaw & Co., L.L.C., which in turn is the managing
member of D. E. Shaw Oculus Portfolios, L.L.C., David E. Shaw may be deemed to
have the shared power to vote or direct the vote of, and the shared power to
dispose or direct the disposition of, the 5,950,800 shares as described above
constituting 5.4% of the outstanding shares and, therefore, David E. Shaw may be
deemed to be the beneficial owner of such shares. David E. Shaw disclaims
beneficial ownership of such 5,950,800 shares.


ITEM 5.        OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS
Not Applicable

ITEM 6.        OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON.
Not Applicable

ITEM 7.        IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH
               ACQUIRED THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING
               COMPANY OR CONTROL PERSON.
Not Applicable

ITEM 8.        IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP
Not Applicable

ITEM 9.        NOTICE OF DISSOLUTION OF GROUP
Not Applicable

ITEM 10.      CERTIFICATION
By signing below, each of D. E. Shaw & Co., L.P. and David E. Shaw certify that,
to the best of such reporting person's knowledge and belief, the securities
referred to above were not acquired and are not held for the purpose of or with
the effect of changing or influencing the control of the issuer of the
securities and were not acquired and are not held in connection with or as a
participant in any transaction having such purposes or effect.



SIGNATURE

After reasonable inquiry and to the best of their knowledge and belief, the
undersigned certify that the information set forth in this statement is true,
complete and correct. A Power of Attorney, dated February 24, 2004, granted by
David E. Shaw in favor of Eric Wepsic, is attached hereto.

Dated: April 10, 2006



                                          D. E. Shaw & Co., L.P.

                                          By: /s/ Eric Wepsic
                                              ---------------
                                              Eric Wepsic
                                              Managing Director



                                          David E. Shaw

                                          By: /s/ Eric Wepsic
                                              ---------------
                                              Eric Wepsic
                                              Attorney-in-Fact for David E. Shaw




                                    EXHIBIT 1

                                POWER OF ATTORNEY
                               FOR CERTAIN FILINGS
                    UNDER THE SECURITIES EXCHANGE ACT OF 1934


I, David E. Shaw, hereby make, constitute and appoint each of:


         Anne Dinning,

         Julius Gaudio,

         Lou Salkind,

         Stuart Steckler, and

         Eric Wepsic,

acting individually, as my agent and attorney-in-fact, with full power of
substitution, for the purpose of, from time to time, executing in my name and/or
my capacity as President of D. E. Shaw & Co., Inc. (acting for itself or as the
general partner of D. E. Shaw & Co., L. P. and general partner or managing
member of other entities, any which in turn may be acting for itself or other
entities) all documents, certificates, instruments, statement, other filings,
and amendments to the forgoing (collectively, "documents") determined by such
person to be necessary or appropriate to comply with ownership or control-person
reporting requirements imposed by any United States or non-United States
governmental or regulatory authority, including without limitation Forms 3, 4,
5, 13D, 13F, and 13G required to be filed with the Securities and Exchange
Commission; and delivering, furnishing or filing any such documents with the
appropriate governmental or regulatory authority. Any such determination shall
be conclusively evidenced by such person's execution, delivery, furnishing,
and/or filing of the applicable document.

This power of attorney shall be valid from the date hereof and replaces the
power granted on February 5, 2001, which is hereby cancelled.

IN WITNESS HEREOF, I have executed this instrument as of the date set forth
below.

Date: February 24, 2004

DAVID E. SHAW, as President of
D. E. Shaw & Co., Inc.
/s/David E. Shaw
New York, New York



                                    EXHIBIT 2

                             JOINT FILING AGREEMENT

In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934,
as amended, each of the undersigned Reporting Persons hereby agrees to the joint
filing, along with all other such Reporting Persons, on behalf of each of them
of a statement on Schedule 13G (including amendments thereto) with respect to
the Common Stock, $0.01 par value, of AK Steel Holding Corporation, and that
this Agreement be included as an Exhibit to such joint filing. This Agreement
may be executed in any number of counterparts, all of which taken together shall
constitute one and the same instrument.

IN WITNESS WHEREOF, each of the undersigned hereby executes this Agreement as of
this 10th day of April, 2006.




                                          D. E. Shaw & Co., L.P.

                                          By: /s/ Eric Wepsic
                                              ---------------
                                              Eric Wepsic
                                              Managing Director



                                          David E. Shaw

                                          By: /s/ Eric Wepsic
                                              ---------------
                                              Eric Wepsic
                                              Attorney-in-Fact for David E. Shaw