UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                                  SCHEDULE 13G

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

                         UNITED THERAPEUTICS CORPORATION
--------------------------------------------------------------------------------
                                (Name of Issuer)

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

                                    91307C102
                                    ---------
                                 (CUSIP Number)

                                February 23, 2006
                                -----------------
                      (Date of Event which Requires Filing
                               of this Statement)



Check the appropriate box to designate the rule pursuant to which this 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 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).







--------------------------------------           -------------------------------
CUSIP No. 91307C102                       13G    Page  2  of 10  Pages
--------------------------------------           -------------------------------

---------- ---------------------------------------------------------------------
        1  NAME OF REPORTING PERSON
           I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

           S.A.C. Capital Advisors, LLC
---------- ---------------------------------------------------------------------
        2  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                     (a) [ ]
                                                                     (b) [X]

---------- ---------------------------------------------------------------------
        3  SEC USE ONLY
---------- ---------------------------------------------------------------------
        4  CITIZENSHIP OR PLACE OF ORGANIZATION

           Delaware
--------------------- ----- ----------------------------------------------------
                         5  SOLE VOTING POWER

                            0
      NUMBER OF       ----- ----------------------------------------------------
       SHARES            6  SHARED VOTING POWER
     BENEFICIALLY
        OWNED               86,454 (see Item 4)
       BY EACH        ----- ----------------------------------------------------
      REPORTING          7  SOLE DISPOSITIVE POWER
    PERSON WITH
                             0
                      ----- ----------------------------------------------------
                         8  SHARED DISPOSITIVE POWER

                            86,454 (see Item 4)
---------- ---------------------------------------------------------------------
        9  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

           86,454 (see Item 4)
---------- ---------------------------------------------------------------------
       10  CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

           [ ]

---------- ---------------------------------------------------------------------
       11  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

           0.4% (see Item 4)
---------- ---------------------------------------------------------------------
       12  TYPE OF REPORTING PERSON*

           00
---------- ---------------------------------------------------------------------
                       *SEE INSTRUCTION BEFORE FILLING OUT





--------------------------------------           -------------------------------
CUSIP No. 91307C102                       13G    Page  3  of 10  Pages
--------------------------------------           -------------------------------

---------- ---------------------------------------------------------------------
        1  NAME OF REPORTING PERSON
           I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

           S.A.C. Capital Management, LLC
---------- ---------------------------------------------------------------------
        2  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                     (a) [ ]
                                                                     (b) [X]

---------- ---------------------------------------------------------------------
        3  SEC USE ONLY
---------- ---------------------------------------------------------------------
        4  CITIZENSHIP OR PLACE OF ORGANIZATION

           Delaware
--------------------- ----- ----------------------------------------------------
                         5  SOLE VOTING POWER

                            0
      NUMBER OF       ----- ----------------------------------------------------
       SHARES            6  SHARED VOTING POWER
     BENEFICIALLY
        OWNED               86,454 (see Item 4)
       BY EACH        ----- ----------------------------------------------------
      REPORTING          7  SOLE DISPOSITIVE POWER
    PERSON WITH
                             0
                      ----- ----------------------------------------------------
                         8  SHARED DISPOSITIVE POWER

                            86,454 (see Item 4)
---------- ---------------------------------------------------------------------
        9  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

           86,454 (see Item 4)
---------- ---------------------------------------------------------------------
       10  CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

           [ ]

---------- ---------------------------------------------------------------------
       11  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

           0.4% (see Item 4)
---------- ---------------------------------------------------------------------
       12  TYPE OF REPORTING PERSON*

           00
---------- ---------------------------------------------------------------------
                       *SEE INSTRUCTION BEFORE FILLING OUT




--------------------------------------           -------------------------------
CUSIP No. 91307C102                       13G    Page  4  of 10  Pages
--------------------------------------           -------------------------------

---------- ---------------------------------------------------------------------
        1  NAME OF REPORTING PERSON
           I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

           Sigma Capital Management, LLC
---------- ---------------------------------------------------------------------
        2  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                     (a) [ ]
                                                                     (b) [X]

---------- ---------------------------------------------------------------------
        3  SEC USE ONLY
---------- ---------------------------------------------------------------------
        4  CITIZENSHIP OR PLACE OF ORGANIZATION

           Delaware
--------------------- ----- ----------------------------------------------------
                         5  SOLE VOTING POWER

                            0
      NUMBER OF       ----- ----------------------------------------------------
       SHARES            6  SHARED VOTING POWER
     BENEFICIALLY
        OWNED               320,000 (see Item 4)
       BY EACH        ----- ----------------------------------------------------
      REPORTING          7  SOLE DISPOSITIVE POWER
    PERSON WITH
                             0
                      ----- ----------------------------------------------------
                         8  SHARED DISPOSITIVE POWER

                            320,000 (see Item 4)
---------- ---------------------------------------------------------------------
        9  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

           320,000 (see Item 4)
---------- ---------------------------------------------------------------------
       10  CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

           [ ]

---------- ---------------------------------------------------------------------
       11  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

           1.4% (see Item 4)
---------- ---------------------------------------------------------------------
       12  TYPE OF REPORTING PERSON*

           00
---------- ---------------------------------------------------------------------
                       *SEE INSTRUCTION BEFORE FILLING OUT




--------------------------------------           -------------------------------
CUSIP No. 91307C102                       13G    Page  5  of 10  Pages
--------------------------------------           -------------------------------

---------- ---------------------------------------------------------------------
        1  NAME OF REPORTING PERSON
           I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

           Steven A. Cohen
---------- ---------------------------------------------------------------------
        2  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                     (a) [ ]
                                                                     (b) [X]

---------- ---------------------------------------------------------------------
        3  SEC USE ONLY
---------- ---------------------------------------------------------------------
        4  CITIZENSHIP OR PLACE OF ORGANIZATION

           United States
--------------------- ----- ----------------------------------------------------
                         5  SOLE VOTING POWER

                            0
      NUMBER OF       ----- ----------------------------------------------------
       SHARES            6  SHARED VOTING POWER
     BENEFICIALLY
        OWNED               406,454 (see Item 4)
       BY EACH        ----- ----------------------------------------------------
      REPORTING          7  SOLE DISPOSITIVE POWER
    PERSON WITH
                            0
                      ----- ----------------------------------------------------
                         8  SHARED DISPOSITIVE POWER

                            406,454 (see Item 4)
---------- ---------------------------------------------------------------------
        9  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

           406,454 (see Item 4)
---------- ---------------------------------------------------------------------
       10  CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

           [ ]

---------- ---------------------------------------------------------------------
       11  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

           1.7% (see Item 4)
---------- ---------------------------------------------------------------------
       12  TYPE OF REPORTING PERSON*

           IN
---------- ---------------------------------------------------------------------
                       *SEE INSTRUCTION BEFORE FILLING OUT



Item 1(a)           Name of Issuer:
                    --------------

                    United Therapeutics Corporation

Item 1(b)           Address of Issuer's Principal Executive Offices:
                    -----------------------------------------------

                    1110 Spring Street
                    Silver Spring, MD  20910

Items 2(a)          Name of Person Filing:
                    ----------------------

                    This statement is filed by: (i) S.A.C. Capital Advisors,
                    LLC, ("SAC Capital Advisors") with respect to shares of
                    common stock, par value $0.01 per share ("Shares") of the
                    Issuer beneficially owned by S.A.C. MultiQuant Fund, LLC
                    ("SAC MultiQuant"); (ii) S.A.C. Capital Management, LLC,
                    ("SAC Capital Management") with respect to Shares
                    beneficially owned by SAC MultiQuant; (iii) Sigma Capital
                    Management, LLC ("Sigma Management") with respect to Shares
                    beneficially owned by Sigma Capital Associates, LLC ("Sigma
                    Capital Associates") and (iv) Steven A. Cohen with respect
                    to Shares beneficially owned by SAC Capital Advisors, SAC
                    Capital Management, SAC MultiQuant, Sigma Management and
                    Sigma Capital Associates.

Item 2(b)           Address of Principal Business Office:
                    -------------------------------------

                    The address of the principal business office of (i) SAC
                    Capital Advisors, and Mr. Cohen is 72 Cummings Point Road,
                    Stamford, Connecticut 06902 and (ii) SAC Capital Management
                    and Sigma Management is 540 Madison Avenue, New York, New
                    York 10022.

Item 2(c)           Citizenship:
                    ------------

                    SAC Capital Advisors, SAC Capital Management and Sigma
                    Management are Delaware limited liability companies. Mr.
                    Cohen is a United States citizen.

Item 2(d)           Title of Class of Securities:
                    -----------------------------

                    Common Stock, par value $0.01 per share

Item 2(e)           CUSIP Number:
                    -------------

                    91307C102

Item 3              Not Applicable


                                  Page 6 of 10


Item 4              Ownership:
                    ----------

                    The percentages used herein are calculated based upon the
                    Shares issued and outstanding as of February 21, 2006 as
                    reported on the Issuer's annual report on Form 10-K filed
                    with the Securities and Exchange Commission by the Company
                    for the fiscal year ended December 31, 2005.

                    As of the close of business on March 2, 2006:

                    1. S.A.C. Capital Advisors, LLC
                    (a)    Amount beneficially owned: 86,454
                    (b)    Percent of class: 0.4%
                    (c)(i) Sole power to vote or direct the vote: -0-
                    (ii)   Shared power to vote or direct the vote: 86,454
                    (iii)  Sole power to dispose or direct the disposition: -0-
                    (iv)   Shared power to dispose or direct the disposition:
                           86,454

                    2. S.A.C. Capital Management, LLC
                    (a)    Amount beneficially owned: 86,454
                    (b)    Percent of class: 0.4%
                    (c)(i) Sole power to vote or direct the vote: -0-
                    (ii)   Shared power to vote or direct the vote: 86,454
                    (iii)  Sole power to dispose or direct the disposition: -0-
                    (iv)   Shared power to dispose or direct the disposition:
                           86,454

                    3. Sigma Capital Management, LLC
                    (a)    Amount beneficially owned: 320,000
                    (b)    Percent of class: 1.4%
                    (c)(i) Sole power to vote or direct the vote: -0-
                    (ii)   Shared power to vote or direct the vote: 320,000
                    (iii)  Sole power to dispose or direct the disposition: -0-
                    (iv)   Shared power to dispose or direct the disposition:
                           320,000

                    4. Steven A. Cohen
                    (a)    Amount beneficially owned: 406,454
                    (b)    Percent of class: 1.7%
                    (c)(i) Sole power to vote or direct the vote: -0-
                    (ii)   Shared power to vote or direct the vote: 406,454
                    (iii)  Sole power to dispose or direct the disposition: -0-
                    (iv)   Shared power to dispose or direct the disposition:
                           406,454

                                  Page 7 of 10


                    SAC Capital Advisors, SAC Capital Management, Sigma
                    Management and Mr. Cohen own directly no Shares. Pursuant to
                    investment agreements, each of SAC Capital Advisors and SAC
                    Capital Management share all investment and voting power
                    with respect to the securities held by SAC MultiQuant.
                    Pursuant to an investment management agreement, Sigma
                    Management maintains investment and voting power with
                    respect to the securities held by Sigma Capital Associates.
                    Mr. Cohen controls each of SAC Capital Advisors, SAC Capital
                    Management and Sigma Management. By reason of the provisions
                    of Rule 13d-3 of the Securities Exchange Act of 1934, as
                    amended, each of (i) SAC Capital Advisors, SAC Capital
                    Management and Mr. Cohen may be deemed to own beneficially
                    86,454 Shares (constituting approximately 0.4% of the Shares
                    outstanding) and (ii) Sigma Management and Mr. Cohen may be
                    deemed to own beneficially 320,000 shares (constituting
                    approximately 1.4% of the Shares outstanding). Each of SAC
                    Capital Advisors, SAC Capital Management, Sigma Management
                    and Mr. Cohen disclaim beneficial ownership of any of the
                    securities covered by this statement.

Item 5              Ownership of Five Percent or Less of a Class:
                    -------------------------------------------

                    If this statement is being filed to report the fact that as
                    of the date hereof the reporting person has ceased to be the
                    beneficial owner of more than five percent of the class of
                    securities, check the following.  [X]

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:
                    -----------------------------------------

                    Not Applicable

Item 8              Identification and Classification of Members
                    ---------------------------------------------
                    of the Group:
                    ------------

                    Not Applicable

Item 9              Notice of Dissolution of Group:
                    ------------------------------

                    Not Applicable

                                 Page 8 of 10


Item 10             Certification:
                    --------------

     By signing below the signatory certifies that, to the best of his 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 that purpose or
effect.

                                  Page 9 of 10



                                    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:  March 3, 2006

S.A.C. CAPITAL ADVISORS, LLC


By: /s/ Peter Nussbaum
   -----------------------------------------
Name:  Peter Nussbaum
Title: Authorized Person



S.A.C. CAPITAL MANAGEMENT, LLC


By: /s/ Peter Nussbaum
   -----------------------------------------
Name:  Peter Nussbaum
Title: Authorized Person



SIGMA CAPITAL MANAGEMENT, LLC


By: /s/ Peter Nussbaum
   -----------------------------------------
Name:  Peter Nussbaum
Title: Authorized Person



STEVEN A. COHEN


By: /s/ Peter Nussbaum
   -----------------------------------------
Name:  Peter Nussbaum
Title: Authorized Person

                                  Page 10 of 10