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 securities       registration of a class of
pursuant to Section 12(b) of the            securities pursuant to Section 12(g)
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
      June [ ], 2010 (Linked to the                American Stock Exchange
      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 April 25, 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,
filed 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 June [ ], 2010
                           (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: May 21, 2003                   By: /s/ Jeffrey Sparks
                                         ----------------------------
                                         Jeffrey Sparks
                                         Managing Director Equities

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