UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                              Washington, DC 20549

                                 SCHEDULE 13G/A
                                 (Rule 13d-102)
                                (Amendment No. 1)
           INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO
            RULES 13d-1(b), (c) AND (d) AND AMENDMENTS THERETO FILED
                            PURSUANT TO RULE 13d-2(b)





                               UNDER ARMOUR, INC.
--------------------------------------------------------------------------------
                                (Name of Issuer)


                   Class A Common Stock, $0.0003 1/3 par value
--------------------------------------------------------------------------------
                         (Title of Class of Securities)


                                    904311107
--------------------------------------------------------------------------------
                                 (CUSIP Number)


                                January 31, 2008
--------------------------------------------------------------------------------
             (Date of Event Which Requires Filing of this Statement)


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

     [X]   Rule 13d-1(b)
     [_]   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
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).


                                    1 of 10




-----------------------------                        ---------------------------
CUSIP No. 904311107                  13G/A
-----------------------------                        ---------------------------

--------------------------------------------------------------------------------
     1     NAME OF REPORTING PERSONS
           I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)

           Maverick Capital, Ltd. - 75-2482446
--------------------------------------------------------------------------------
     2     CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*    (a)  |_|
                                                                (b)  |_|
--------------------------------------------------------------------------------
     3     SEC USE ONLY

--------------------------------------------------------------------------------
     4     CITIZENSHIP OR PLACE OF ORGANIZATION

           Texas
--------------------------------------------------------------------------------
                |   5   |  SOLE VOTING POWER
                |       |
                |       |  3,779,420
 NUMBER OF      ---------------------------------------------------------------
   SHARES       |   6   |  SHARED VOTING POWER
BENEFICIALLY    |       |
  OWNED BY      |       |  0
    EACH        ----------------------------------------------------------------
 REPORTING      |   7   |  SOLE DISPOSITIVE POWER
PERSON WITH     |       |
                |       |  3,779,420
                ----------------------------------------------------------------
                |   8   |  SHARED DISPOSITIVE POWER
                |       |
                |       |  0
--------------------------------------------------------------------------------
     9     AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

           3,779,420
--------------------------------------------------------------------------------
    10     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES
           CERTAIN SHARES*
                                                                        |_|
--------------------------------------------------------------------------------
    11     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

           10.7%
--------------------------------------------------------------------------------
    12     TYPE OF REPORTING PERSON*

           IA
--------------------------------------------------------------------------------

         *SEE INSTRUCTIONS BEFORE FILLING OUT


                                    2 of 10



-----------------------------                        ---------------------------
CUSIP No. 904311107                  13G/A
-----------------------------                        ---------------------------

--------------------------------------------------------------------------------
     1     NAME OF REPORTING PERSONS
           I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)

           Maverick Capital Management, LLC - 75-2686461
--------------------------------------------------------------------------------
     2     CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*    (a)  |_|
                                                                (b)  |_|
--------------------------------------------------------------------------------
     3     SEC USE ONLY

--------------------------------------------------------------------------------
     4     CITIZENSHIP OR PLACE OF ORGANIZATION

           Texas
--------------------------------------------------------------------------------
                |   5   |  SOLE VOTING POWER
                |       |
                |       |  3,779,420
 NUMBER OF      ---------------------------------------------------------------
   SHARES       |   6   |  SHARED VOTING POWER
BENEFICIALLY    |       |
  OWNED BY      |       |  0
    EACH        ----------------------------------------------------------------
 REPORTING      |   7   |  SOLE DISPOSITIVE POWER
PERSON WITH     |       |
                |       |  3,779,420
                ----------------------------------------------------------------
                |   8   |  SHARED DISPOSITIVE POWER
                |       |
                |       |  0
--------------------------------------------------------------------------------
     9     AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

           3,779,420
--------------------------------------------------------------------------------
    10     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES
           CERTAIN SHARES*
                                                                        |_|
--------------------------------------------------------------------------------
    11     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

           10.7%
--------------------------------------------------------------------------------
    12     TYPE OF REPORTING PERSON*

           HC
--------------------------------------------------------------------------------

         *SEE INSTRUCTIONS BEFORE FILLING OUT


                                     3 of 10



-----------------------------                        ---------------------------
CUSIP No. 904311107                  13G/A
-----------------------------                        ---------------------------

--------------------------------------------------------------------------------
     1     NAME OF REPORTING PERSONS
           I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)

           Lee S. Ainslie III
--------------------------------------------------------------------------------
     2     CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*    (a)  |_|
                                                                (b)  |_|
--------------------------------------------------------------------------------
     3     SEC USE ONLY

--------------------------------------------------------------------------------
     4     CITIZENSHIP OR PLACE OF ORGANIZATION

           United States
--------------------------------------------------------------------------------
                |   5   |  SOLE VOTING POWER
                |       |
                |       |  3,779,420
 NUMBER OF      ---------------------------------------------------------------
   SHARES       |   6   |  SHARED VOTING POWER
BENEFICIALLY    |       |
  OWNED BY      |       |  0
    EACH        ----------------------------------------------------------------
 REPORTING      |   7   |  SOLE DISPOSITIVE POWER
PERSON WITH     |       |
                |       |  3,779,420
                ----------------------------------------------------------------
                |   8   |  SHARED DISPOSITIVE POWER
                |       |
                |       |  0
--------------------------------------------------------------------------------
     9     AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

           3,779,420
--------------------------------------------------------------------------------
    10     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES
           CERTAIN SHARES*
                                                                        |_|
--------------------------------------------------------------------------------
    11     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

           10.7%
--------------------------------------------------------------------------------
    12     TYPE OF REPORTING PERSON*

           HC
--------------------------------------------------------------------------------

         *SEE INSTRUCTIONS BEFORE FILLING OUT


                                    4 of 10



Item 1(a)   Name of Issuer.

            Under Armour, Inc.

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

            1020 Hull Street
            Baltimore, Maryland  21230

Item 2(a)   Name of Person Filing.

            This Schedule 13G (the  "Schedule  13G") is being filed on behalf of
            each of the following persons (each, a "Reporting Person"):

            (i)   Maverick Capital, Ltd.;
            (ii)  Maverick Capital Management, LLC; and
            (iii) Lee S. Ainslie III ("Mr. Ainslie").

            The Schedule 13G relates to Shares (as defined  herein) held for the
            accounts of Maverick Capital, Ltd.'s clients.

Item 2(b)   Address of Principal Business Office, or, if none, Residence.

            The  address  of the  principal  business  office  of  (i)  Maverick
            Capital,  Ltd. and Maverick Capital Management,  LLC is 300 Crescent
            Court, 18th Floor,  Dallas, Texas 75201, and (ii) Mr. Ainslie is 767
            Fifth Avenue, 11th Floor, New York, New York 10153.

Item 2(c)   Citizenship or Place of Organization.

            (i)   Maverick Capital, Ltd. is a Texas limited partnership;
            (ii)  Maverick Capital Management, LLC is a Texas limited liability
                  company; and
            (iii) Mr. Ainslie is a citizen of the United States.

Item 2(d)   Title of Class of Securities.

            Class A Common Stock, $0.0003 1/3 par value (the "Shares").

Item 2(e)   CUSIP Number.

            904311107


                                    5 of 10



Item 3.     If this  statement  is filed  pursuant to  ss.ss.240.13d-1(b)  or
            240.13d-2(b) or (c), check whether the person filing is a:

   (a)  [_] Broker or dealer registered under section 15 of the Act (15
            U.S.C. 78o).

   (b)  [_] Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

   (c)  [_] Insurance  company as defined  in  section  3(a)(19)  of the Act (15
            U.S.C. 78c).

   (d)  [_] Investment  company  registered  under  section 8 of the  Investment
            Company Act of 1940 (15 U.S.C. 80a-8).

   (e)  [X] An investment advisor in accordance with ss.240.13d-1(b)(1)(ii)(E).

   (f)  [_] An  employee  benefit  plan or  endowment  fund in  accordance  with
            ss.240.13d-1(b)(1)(ii)(F).

   (g)  [X] A parent  holding  company  or  control  person in  accordance  with
            ss.240.13d-1(b)(1)(ii)(G).

   (h)  [_] A savings  association  as defined in  Section  3(b) of the  Federal
            Deposit Insurance Act (12 U.S.C. 1813).

   (i)  [_] A church plan that is excluded from the  definition of an investment
            company under Section 3(c)(14) of the Investment Company Act of 1940
            (15 U.S.C. 80a-3).

   (j)  [_] Group, in accordance with ss.240.13d-1(b)(1)(ii)(J).

Item 4      Ownership.

            Ownership  as of January 31, 2008 is  incorporated  by  reference to
            items (5) - (9) and (11) of the cover page of the Reporting Person.

            Maverick  Capital,  Ltd. is an investment  adviser  registered under
            Section 203 of the Investment Advisers Act of 1940 and, as such, may
            be deemed to have  beneficial  ownership of the Shares which are the
            subject  of  this  filing  through  the  investment   discretion  it
            exercises over its clients' accounts.  Maverick Capital  Management,
            LLC is the General Partner of Maverick Capital,  Ltd. Mr. Ainslie is
            a manager of Maverick  Capital  Management,  LLC and is granted sole
            investment discretion pursuant to Maverick Capital Management, LLC's
            Regulations.

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.

            Not applicable.


                                    6 of 10



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 the Reporting  Persons  certifies  that, to
            the best of such  person's  knowledge,  and belief,  the  securities
            referred to above were acquired and are held in the ordinary  course
            of business  and 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.


                                    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.

Date:  February 11, 2008             MAVERICK CAPITAL, LTD.

                                     By:   Maverick Capital Management, LLC,
                                           Its General Partner

                                           By: Lee S. Ainslie III, Manager

                                               By: /s/ John T. McCafferty
                                                   -----------------------------
                                                   John T. McCafferty
                                                   Under Power of Attorney dated
                                                   February 13, 2003

Date:  February 11, 2008             MAVERICK CAPITAL MANAGEMENT, LLC

                                     By:   Lee S. Ainslie III, Manager

                                           By: /s/ John T. McCafferty
                                               ---------------------------------
                                               John T. McCafferty
                                               Under Power of Attorney dated
                                               February 13, 2003



                                    7 of 10





Date:  February 11, 2008             LEE S. AINSLIE III


                                       By: /s/ John T. McCafferty
                                           -------------------------------------
                                           John T. McCafferty
                                           Under Power of Attorney dated
                                           February 13, 2003




                                    8 of 10




                                  EXHIBIT INDEX

A.    Joint Filing  Agreement,  dated  February 11, 2008, by and among  Maverick
      Capital, Ltd., Maverick Capital Management, LLC, and Lee S. Ainslie III.








                                    9 of 10





                                                                       Exhibit A

                             Joint Filing Agreement

      The  undersigned  hereby  agree that the  statement  on Schedule  13G with
respect  to the Class A Common  Stock,  $0.0003  1/3 par value of Under  Armour,
Inc., dated as of February 11, 2008, is, and any amendments  thereto  (including
amendments on Schedule 13D) signed by each of the undersigned shall be, filed on
behalf of each of us pursuant to and in accordance  with the  provisions of Rule
13d-1(k) under the Securities Exchange Act of 1934.

Date: February 11, 2008


                             MAVERICK CAPITAL, LTD.

                              By: Maverick Capital Management, LLC
                                  Its General Partner

                                  By: Lee S. Ainslie III, Manager



                                      By: /s/ John T. McCafferty
                                          ------------------------------
                                          John  T.  McCafferty
                                          Under Power of Attorney dated
                                          February 13, 2003


                              MAVERICK CAPITAL MANAGEMENT, LLC

                              By: Lee S. Ainslie III, Manager



                                  By: /s/ John T. McCafferty
                                      ----------------------------------
                                      John T. McCafferty
                                      Under Power of Attorney dated
                                      February 13, 2003


                              LEE S. AINSLIE III



                              By: /s/ John T. McCafferty
                                  --------------------------------------
                                  John T.  McCafferty
                                  Under Power of Attorney dated
                                  February 13, 2003