SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549

                                    FORM 8-A

                FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES
                    PURSUANT TO SECTION 12(b) OR 12(g) OF THE
                         SECURITIES EXCHANGE ACT OF 1934

                                     UBS AG
- --------------------------------------------------------------------------------
             (Exact Name of Registrant as Specified in Its Charter)

              Switzerland                                      98-0186363
- ----------------------------------------------          ------------------------
   (State of Incorporation or Organization)                 (I.R.S. Employer
                                                           Identification no.)

     Bahnhofstrasse 45, Zurich and
        Aeschenvorstadt 1, Basel
- ----------------------------------------------          ------------------------
   (Address or Principal Executive Offices)                    (Zip Code)

   If this form relates to the              If this form relates to the
   registration of a class of               registration of a class of
   securities pursuant to Section 12(b)     securities pursuant to Section 12(g)
   of the Exchange Act and is effective     of the Exchange Act and is effective
   pursuant to General Instruction          pursuant to General Instruction
   A.(c), please check the following        A.(d), please check the following
   box: [X]                                 box: [ ]

Securities Act registration statement file number to which this form relates:

                                                                    333-64844
                                                                 ---------------
                                                                 (If applicable)

Securities to be registered pursuant to Section 12(b) of the Act:

         Title of Each Class                   Name of Each Exchange on Which
         To be so Registered                   Each Class is to be Registered
- ---------------------------------------     ------------------------------------

   Principal Protected Notes due            American Stock Exchange
   October [ ], 2009 (Linked to the
  performance of the S&P 500(R)Index)
- ---------------------------------------     ------------------------------------

Securities to be registered pursuant to Section 12(g) of the Act:

                                      None
- --------------------------------------------------------------------------------
                                (Title of Class)



INFORMATION REQUIRED IN REGISTRATION STATEMENT

ITEM 1.        DESCRIPTION OF REGISTRANT'S SECURITIES TO BE REGISTERED

               UBS AG (the "Company") hereby incorporates by reference the
description of its securities to be registered hereunder contained in the
Preliminary Prospectus Supplement filed with the Commission on March 7, 2003
under Rule 424(b)(2) and in the Prospectus dated February 27, 2003 under
"Description of Debt Securities We May Offer" pursuant to an effective
Registration Statement on Form F-3 (File No. 333-64844) (the "Additional
Registration Statement") under the Securities Act of 1933, as amended, filed
with the Commission on December 19, 2002; the Additional Registration Statement,
pursuant to Rule 429 under the Securities Act, constitutes Post-Effective
Amendment No. 4 to the Company's Registration Statement on Form F-1 (File No.
333-46930) (the "Prior Registration Statement") filed with the Commission on
September 29, 2000, as previously amended by Post-Effective Amendment No. 1
thereto on Form F-1 filed with the Commission on March 23, 2001, by
Post-Effective Amendment No. 2 thereto on Form F-1 filed with the Commission on
March 29, 2001 and by Post-Effective Amendment No. 3 thereto on Form F-3 filed
with the Commission on May 15, 2001.

ITEM 2.        EXHIBITS.

               1.   Debt Indenture, dated as of November 21, 2000, between the
                    Company and U.S. Bank Trust National Association, as debt
                    trustee, including form of debt securities (included as
                    Exhibit 4.1 to the Prior Registration Statement)

               2.   Form of Principal Protected Notes due October [ ],
                    2009 (Linked to the performance of the S&P 500(R)Index)



               3.   SIGNATURE

               Pursuant to the requirements of Section 12 of the Securities
Exchange Act of 1934, the registrant has duly caused this registration statement
to be signed on its behalf by the undersigned, thereto duly authorized.

                                                        UBS AG
                                                        (Registrant)

Date: March 31, 2003                                    By: /s/ Jeffrey Sparks
                                                           ---------------------
                                                           Jeffrey Sparks
                                                           Managing Director
                                                           Equities

                                                        By: /s/ Michael Mahaffy
                                                           ---------------------
                                                           Michael Mahaffy
                                                           Managing Director
                                                           Equities