<PAGE>
     As filed with the Securities and Exchange Commission on August 4, 2005

                                                 Registration No. 333-__________

================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                   ----------

                                    FORM S-8

                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                                   ----------

                                     UBS AG
             (Exact name of registrant as specified in its charter)

<TABLE>
<S>                                                          <C>
          SWITZERLAND                                             98-0186363
(State or other jurisdiction of                                (I.R.S. Employer
 incorporation or organization)                              Identification No.)
</TABLE>

                   BAHNHOFSTRASSE 45, ZURICH, SWITZERLAND, AND
                      AESCHENVORSTADT 1, BASEL, SWITZERLAND
                    (Address of Principal Executive Offices)

                            UBS AG OMNIBUS STOCK PLAN
                            (Full title of the Plan)

                                   JAMES ODELL
                                     UBS AG
                                  299 PARK AVE.
                            NEW YORK, NEW YORK 10171
                                 (212) 821-3000
            (Name, address and telephone number of agent for service)

================================================================================
<PAGE>
                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
                                             Proposed maximum    Proposed maximum      Amount of
Title of securities to be    Amount to be     offering price    aggregate offering   registration
        registered            registered         per unit              price              fee
-------------------------   --------------   ----------------   ------------------   ------------
<S>                         <C>              <C>                <C>                  <C>
Ordinary Shares, par        95,000,000 (2)      $83.815          $7,962,425,000        $937,177.42
value CHF 0.80 (1)
</TABLE>

(1)  The Ordinary Shares par value CHF 0.80 (the "Ordinary Shares") of UBS AG
     (the "Company" or the "Registrant") being registered hereunder will be
     issued pursuant to the UBS AG Omnibus Stock Plan (the "Plan").

(2)  Such indeterminate number of additional shares as may be issuable pursuant
     to a recapitalization of the Ordinary Shares under the Plan is hereby also
     registered.

(3)  Pursuant to Rule 457(c) and Rule 457(h) under the Securities Act of 1933
     (the "Securities Act"), the proposed maximum offering price and the
     registration fee have been computed on the basis of an assumed price of
     $83.815 per share, which was the average of the high and low prices of
     Ordinary Shares as reported on the New York Stock Exchange Consolidated
     Tape on August 3, 2005.


                                       2
<PAGE>
              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

                                EXPLANATORY NOTE

     As permitted by Rule 428 under the Securities Act, this registration
statement omits the information specified in Part I of Form S-8. The documents
containing the information specified in Part I will be delivered to the
participants in the Plan covered by this registration statement, as required by
Rule 428(b) under the Securities Act. Such documents are not being filed with
the Securities and Exchange Commission (the "Commission") as part of this
registration statement or as prospectuses or prospectus supplements pursuant to
Rule 424 of the Securities Act.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3. Incorporation of Documents by Reference

          Incorporated by reference in this Registration Statement are the
following documents filed by the Company with the Commission pursuant to the
Securities Exchange Act of 1934, as amended (the "Exchange Act"):

     a.   The Company's Annual Report on Form 20-F for the year ended December
          31, 2004 (File No. 001-15060), filed pursuant to the Exchange Act;

     b.   The Company's reports on Form 6-K (File No. 001-15060), submitted to
          the Commission on June 30, 2005, May 4, 2005, and April 21, 2005; and

     c.   The description of the Ordinary Shares contained in the Company's
          Annual Report on Form 20-F filed with the Commission on May 9, 2000,
          pursuant to the Exchange Act (Registration No. 001150226), and any
          amendment or report filed for the purpose of updating such
          description.

          In addition, to the extent designated therein, certain reports on Form
6-K and all documents subsequently filed by the Company pursuant to sections
13(a), 13(c), 14 or 15(d) of the Exchange Act, prior to the filing of a
post-effective amendment that indicates that all securities offered hereby have
been sold or that deregisters all such securities then remaining unsold, shall
be deemed to be incorporated by reference in this Registration Statement and to
be part hereof from the dates of filing of such documents.

          Any statement contained in a document incorporated or deemed to be
incorporated by reference herein shall be deemed to be modified or superseded
for purposes of this registration statement to the extent that a statement
contained herein (or


                                       3
<PAGE>
in any other subsequently filed document which also is incorporated or deemed to
be incorporated by reference herein) modifies or supersedes such statement. Any
such statement so modified or superseded shall not be deemed, except as so
modified or superseded, to constitute a part of this registration statement.

Item 4. Description of Securities

          Not applicable.

Item 5. Interests of Named Experts and Counsel

          Not applicable.

Item 6. Indemnification of Directors and Officers

          Under Swiss law, directors and senior officers acting in violation of
their statutory duties - whether dealing with bona fide third parties or
performing any other acts on behalf of the corporation - may become liable to
the corporation, its shareholders and (in bankruptcy) its creditors for damages.
The directors' liability is joint and several but only to the extent the damage
is attributable to each director based on willful or negligent violation of
duty. If the board of directors lawfully delegated the power to carry out
day-to-day management to a different corporate body, e.g., the executive board,
the board of directors is not vicariously liable for the acts of the members of
the executive board. Instead the directors can be held liable for their failure
to properly select, instruct or supervise the executive board members. If
directors and officers enter into a transaction on behalf of the corporation
with bona fide third parties in violation of their statutory duties, the
transaction is nevertheless valid as long as it is not excluded by the
corporation's business purpose.

          Under Swiss law, a corporation may indemnify a director or officer of
the corporation against losses and expenses (unless arising from his gross
negligence or willful misconduct), including attorney's fees, judgments, fines
and settlement amounts actually and reasonably incurred in a civil or criminal
action, suit or proceeding by reason of having been the representative of or
serving at the request of the corporation.

          Because the Company is a Swiss company headquartered in Switzerland,
many of the directors and officers of the Company are residents of Switzerland
and not the U.S. As a result, U.S. investors may find it difficult in a lawsuit
based on the civil liability provisions of the U.S. federal securities laws to:

          -    effect service within the U.S. upon the Company and the directors
               and officers of the Company located outside the U.S.,


                                       4
<PAGE>
          -    enforce in U.S. courts or outside the U.S. judgments obtained
               against those persons in U.S. courts,

          -    enforce in U.S. courts, judgments obtained against those persons
               in courts in jurisdictions outside the U.S., and

          -    enforce against those persons in Switzerland, whether in original
               actions or in actions for the enforcement of judgments of U.S.
               courts, civil liabilities based solely upon the U.S. federal
               securities laws.

          Neither the Company's articles of association nor Swiss statutory law
contain provisions regarding the indemnification of directors and officers.

          According to general principles of Swiss employment law, an employer
may, under certain circumstances, be required to indemnify an employee against
losses and expenses incurred by him in the execution of his duties under an
employment agreement, unless the losses and expenses arise from the employee's
gross negligence or willful misconduct.

          The Company maintains directors' and officers' insurance for its
directors and officers.

Item 7. Exemption from Registration Claimed

          Not applicable.

Item 8. Exhibits

          An Exhibit Index, containing a list of all exhibits filed with this
registration statement, is included on page 8.

Item 9. Undertakings

          (a) Rule 415 Offering. The undersigned Registrant hereby undertakes:

          (1) To file, during any period in which offers or sales are being
     made, a post-effective amendment to this Registration Statement, which
     will:

               (i) include any Prospectus required by Section 10(a)(3) of the
          Securities Act, unless the information is contained in periodic
          reports filed by the Registrant pursuant to Section 13 or Section
          15(d) of the Exchange Act that are incorporated by reference in the
          Registration Statement;


                                       5
<PAGE>
               (ii) reflect in the Prospectus any facts or events arising after
          the effective date of the Registration Statement (or the most recent
          post-effective amendment thereof) which, individually or in the
          aggregate, represent a fundamental change in the information set forth
          in the Registration Statement. Notwithstanding the foregoing, any
          increase or decrease in volume of securities offered (if the total
          dollar value of securities offered would not exceed that which was
          registered) and any deviation from the low or high end of the
          estimated maximum offering range may be reflected in the form of
          prospectus filed with the Commission pursuant to Rule 424(b) of the
          Securities Act, if, in the aggregate, the changes in volume and price
          represent no more than a 20% change in the maximum aggregate offering
          price set forth in the "Calculation of Registration Fee" table in the
          effective registration statement;

               (iii) include any material information with respect to the plan
          of distribution not previously disclosed in the registration statement
          or any material change to such information in the registration
          statement;

          provided, however, that paragraphs 9(a)(1)(i) and 9(a)(1)(ii) do not
          apply if the registration statement is on Form S-3 or Form S-8, and
          the information required to be included in a post-effective amendment
          by those paragraphs is contained in periodic reports filed by the
          registrant pursuant to section 13 or section 15(d) of the Exchange Act
          that are incorporated by reference in the registration statement.

          (2) That, for the purpose of determining any liability under the
     Securities Act, each such post-effective amendment shall be deemed to be a
     new registration statement relating to the securities offered therein, and
     the offering of such securities at that time shall be deemed to be the
     initial bona fide offering thereof.

          (3) To remove from registration by means of a post-effective amendment
     any of the securities being registered which remain unsold at the
     termination of the offering.

          (b) Subsequent Exchange Act Documents. The undersigned Registrant
hereby undertakes that, for purposes of determining any liability under the
Securities Act, each filing of the Registrant's annual report pursuant to
section 13(a) or section 15(d) of the Exchange Act (and, where applicable, each
filing of an employee benefit plan's annual report pursuant to section 15(d) of
the Exchange Act) that is incorporated by reference in the Registration
Statement shall be deemed to be a new


                                       6
<PAGE>
registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

          (c) Indemnification. Insofar as indemnification for liabilities
arising under the Securities Act may be permitted to directors, officers and
controlling persons of the Registrant pursuant to the foregoing provisions, or
otherwise, the Registrant has been advised that in the opinion of the Commission
such indemnification is against public policy as expressed in the Securities Act
and is, therefore, unenforceable. In the event that a claim for indemnification
against such liabilities (other than the payment by the Registrant of expenses
incurred or paid by a director, officer or controlling person of the Registrant
in the successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the Registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the Securities Act and will be governed by the final
adjudication of such issue.


                                       7
<PAGE>
                                Index to Exhibits

<TABLE>
<CAPTION>
Exhibit No.                         Description of Exhibit
-----------                         ----------------------
<S>           <C>
4.1           Articles of Association of UBS AG (incorporated by reference to
              Exhibit 1.1 to the Company's Annual Report on Form 20-F for the
              fiscal year ended 31 December 2004).

4.2           Organization Regulations of UBS AG (incorporated by reference to
              Exhibit 1.2 to the Company's Annual Report on Form 20-F for the
              fiscal year ended 31 December 2004).

4.3           Instruments defining the rights of holders of long-term debt
              issued by UBS AG and its subsidiaries (incorporated by reference
              to Exhibit 2(b) to the Company's Annual Report on Form 20-F for
              the fiscal year ended 31 December 2004).

23.1          Consent of Ernst & Young Ltd.

24            Powers of Attorney.
</TABLE>


                                        8
<PAGE>
                                   SIGNATURES

          The Registrant. Pursuant to the requirements of the Securities Act of
1933, the Registrant certifies that it has reasonable grounds to believe that it
meets all of the requirements for filing on Form S-8 and has duly caused this
registration statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of Zurich, Switzerland on the 4th day of August
2005.

                                        UBS AG


                                        By: /s/ Hugo Schaub
                                            ------------------------------------
                                        Name: Hugo Schaub
                                        Title: Group Controller


                                        By: /s/ James Odell
                                            ------------------------------------
                                        Name: James Odell
                                        Title: Managing Director

          Pursuant to the requirements of the Securities Act, this registration
statement has been signed by the following persons in the capacities and on the
dates indicated.

<TABLE>
<CAPTION>
          NAME                          TITLE                    DATE
          ----                          -----                    ----
<S>                        <C>                              <C>


/s/ Peter Wuffli                 President of Group         04 August 2005
------------------------           Executive Board
Peter Wuffli                (principal executive officer)


/s/ Clive Standish          Group Chief Financial Officer   04 August 2005
------------------------    (principal financial officer)
Clive Standish


/s/ Hugo Schaub                   Group Controller          04 August 2005
------------------------   (principal accounting officer)
Hugo Schaub


/s/ Marcel Ospel              Chairman of the Board of      04 August 2005
------------------------              Directors
Marcel Ospel


/s/ Stephan Haeringer       Vice Chairman of the Board of   04 August 2005
------------------------              Directors
Stephan Haeringer
</TABLE>
<PAGE>
<TABLE>
<CAPTION>
          NAME                          TITLE                    DATE
          ----                          -----                    ----
<S>                        <C>                              <C>


/s/ Marco Suter             Vice Chairman of the Board of   04 August 2005
------------------------              Directors
Marco Suter


/s/ Peter Bockli             Vice Chairman and Member of    04 August 2005
------------------------         Board of Directors
Peter Bockli


/s/ Ernesto Bertarelli      Member of Board of Directors    04 August 2005
------------------------
Ernesto Bertarelli


/s/ Sir Peter Davis         Member of Board of Directors    04 August 2005
------------------------
Sir Peter Davis


/s/ Rolf A. Meyer           Member of Board of Directors    04 August 2005
------------------------
Rolf A. Meyer


/s/ Helmut Panke            Member of Board of Directors    04 August 2005
------------------------
Helmut Panke


/s/ Peter Spuhler           Member of Board of Directors    04 August 2005
------------------------
Peter Spuhler


/s/ Peter R. Voser          Member of Board of Directors    04 August 2005
------------------------
Peter R. Voser


/s/ Lawrence A. Weinbach    Member of Board of Directors    04 August 2005
------------------------
Lawrence A. Weinbach
</TABLE>
<PAGE>
          Pursuant to the requirements of Section 6(a) of the Securities Act, as
amended, the Authorized Representative has duly caused this Registration
Statement to be signed, solely in his capacity as the duly authorized
representative of UBS AG in the United States, in the City of New York, State of
New York, on the 4th day of August 2005.


                                        By: /s/ James Odell
                                            ------------------------------------
                                        Name: James Odell
                                        Title: Managing Director
[{"type": "S-8", "sequence": "1", "filename": "y11536sv8.txt", "description": "FORM S-8", "secsgml_size_bytes": 19889}]
{"company-data": {"conformed-name": "UBS AG", "cik": "0001114446", "assigned-sic": "6021", "irs-number": "000000000", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-127180", "film-number": "05999179"}, "business-address": {"street1": "BAHNHOFSTRASSE 45", "street2": "P O BOX CH 8098", "city": "ZURICH", "state": "V8", "zip": "-", "phone": "41-1-234-4100"}, "mail-address": {"street1": "BAHNHOFSTRASSE 45", "street2": "P O BOX CH 8098", "city": "ZURICH", "state": "V8", "zip": "-"}}
As filed with the Securities and Exchange Commission on August 4, 2005

                                                 Registration No. 333-__________

================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                   ----------

                                    FORM S-8

                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                                   ----------

                                     UBS AG
             (Exact name of registrant as specified in its charter)
SWITZERLAND                                             98-0186363
(State or other jurisdiction of                                (I.R.S. Employer
 incorporation or organization)                              Identification No.)
BAHNHOFSTRASSE 45, ZURICH, SWITZERLAND, AND
                      AESCHENVORSTADT 1, BASEL, SWITZERLAND
                    (Address of Principal Executive Offices)

                            UBS AG OMNIBUS STOCK PLAN
                            (Full title of the Plan)

                                   JAMES ODELL
                                     UBS AG
                                  299 PARK AVE.
                            NEW YORK, NEW YORK 10171
                                 (212) 821-3000
            (Name, address and telephone number of agent for service)

================================================================================
CALCULATION OF REGISTRATION FEE
Proposed maximum    Proposed maximum      Amount of
Title of securities to be    Amount to be     offering price    aggregate offering   registration
        registered            registered         per unit              price              fee
-------------------------   --------------   ----------------   ------------------   ------------
Ordinary Shares, par        95,000,000 (2)      $83.815          $7,962,425,000        $937,177.42
value CHF 0.80 (1)
(1)  The Ordinary Shares par value CHF 0.80 (the "Ordinary Shares") of UBS AG
     (the "Company" or the "Registrant") being registered hereunder will be
     issued pursuant to the UBS AG Omnibus Stock Plan (the "Plan").

(2)  Such indeterminate number of additional shares as may be issuable pursuant
     to a recapitalization of the Ordinary Shares under the Plan is hereby also
     registered.

(3)  Pursuant to Rule 457(c) and Rule 457(h) under the Securities Act of 1933
     (the "Securities Act"), the proposed maximum offering price and the
     registration fee have been computed on the basis of an assumed price of
     $83.815 per share, which was the average of the high and low prices of
     Ordinary Shares as reported on the New York Stock Exchange Consolidated
     Tape on August 3, 2005.

                                       2
INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

                                EXPLANATORY NOTE

     As permitted by Rule 428 under the Securities Act, this registration
statement omits the information specified in Part I of Form S-8. The documents
containing the information specified in Part I will be delivered to the
participants in the Plan covered by this registration statement, as required by
Rule 428(b) under the Securities Act. Such documents are not being filed with
the Securities and Exchange Commission (the "Commission") as part of this
registration statement or as prospectuses or prospectus supplements pursuant to
Rule 424 of the Securities Act.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3. Incorporation of Documents by Reference

          Incorporated by reference in this Registration Statement are the
following documents filed by the Company with the Commission pursuant to the
Securities Exchange Act of 1934, as amended (the "Exchange Act"):

     a.   The Company's Annual Report on Form 20-F for the year ended December
          31, 2004 (File No. 001-15060), filed pursuant to the Exchange Act;

     b.   The Company's reports on Form 6-K (File No. 001-15060), submitted to
          the Commission on June 30, 2005, May 4, 2005, and April 21, 2005; and

     c.   The description of the Ordinary Shares contained in the Company's
          Annual Report on Form 20-F filed with the Commission on May 9, 2000,
          pursuant to the Exchange Act (Registration No. 001150226), and any
          amendment or report filed for the purpose of updating such
          description.

          In addition, to the extent designated therein, certain reports on Form
6-K and all documents subsequently filed by the Company pursuant to sections
13(a), 13(c), 14 or 15(d) of the Exchange Act, prior to the filing of a
post-effective amendment that indicates that all securities offered hereby have
been sold or that deregisters all such securities then remaining unsold, shall
be deemed to be incorporated by reference in this Registration Statement and to
be part hereof from the dates of filing of such documents.

          Any statement contained in a document incorporated or deemed to be
incorporated by reference herein shall be deemed to be modified or superseded
for purposes of this registration statement to the extent that a statement
contained herein (or

                                       3
in any other subsequently filed document which also is incorporated or deemed to
be incorporated by reference herein) modifies or supersedes such statement. Any
such statement so modified or superseded shall not be deemed, except as so
modified or superseded, to constitute a part of this registration statement.

Item 4. Description of Securities

          Not applicable.

Item 5. Interests of Named Experts and Counsel

          Not applicable.

Item 6. Indemnification of Directors and Officers

          Under Swiss law, directors and senior officers acting in violation of
their statutory duties - whether dealing with bona fide third parties or
performing any other acts on behalf of the corporation - may become liable to
the corporation, its shareholders and (in bankruptcy) its creditors for damages.
The directors' liability is joint and several but only to the extent the damage
is attributable to each director based on willful or negligent violation of
duty. If the board of directors lawfully delegated the power to carry out
day-to-day management to a different corporate body, e.g., the executive board,
the board of directors is not vicariously liable for the acts of the members of
the executive board. Instead the directors can be held liable for their failure
to properly select, instruct or supervise the executive board members. If
directors and officers enter into a transaction on behalf of the corporation
with bona fide third parties in violation of their statutory duties, the
transaction is nevertheless valid as long as it is not excluded by the
corporation's business purpose.

          Under Swiss law, a corporation may indemnify a director or officer of
the corporation against losses and expenses (unless arising from his gross
negligence or willful misconduct), including attorney's fees, judgments, fines
and settlement amounts actually and reasonably incurred in a civil or criminal
action, suit or proceeding by reason of having been the representative of or
serving at the request of the corporation.

          Because the Company is a Swiss company headquartered in Switzerland,
many of the directors and officers of the Company are residents of Switzerland
and not the U.S. As a result, U.S. investors may find it difficult in a lawsuit
based on the civil liability provisions of the U.S. federal securities laws to:

          -    effect service within the U.S. upon the Company and the directors
               and officers of the Company located outside the U.S.,

                                       4
-    enforce in U.S. courts or outside the U.S. judgments obtained
               against those persons in U.S. courts,

          -    enforce in U.S. courts, judgments obtained against those persons
               in courts in jurisdictions outside the U.S., and

          -    enforce against those persons in Switzerland, whether in original
               actions or in actions for the enforcement of judgments of U.S.
               courts, civil liabilities based solely upon the U.S. federal
               securities laws.

          Neither the Company's articles of association nor Swiss statutory law
contain provisions regarding the indemnification of directors and officers.

          According to general principles of Swiss employment law, an employer
may, under certain circumstances, be required to indemnify an employee against
losses and expenses incurred by him in the execution of his duties under an
employment agreement, unless the losses and expenses arise from the employee's
gross negligence or willful misconduct.

          The Company maintains directors' and officers' insurance for its
directors and officers.

Item 7. Exemption from Registration Claimed

          Not applicable.

Item 8. Exhibits

          An Exhibit Index, containing a list of all exhibits filed with this
registration statement, is included on page 8.

Item 9. Undertakings

          (a) Rule 415 Offering. The undersigned Registrant hereby undertakes:

          (1) To file, during any period in which offers or sales are being
     made, a post-effective amendment to this Registration Statement, which
     will:

               (i) include any Prospectus required by Section 10(a)(3) of the
          Securities Act, unless the information is contained in periodic
          reports filed by the Registrant pursuant to Section 13 or Section
          15(d) of the Exchange Act that are incorporated by reference in the
          Registration Statement;

                                       5
(ii) reflect in the Prospectus any facts or events arising after
          the effective date of the Registration Statement (or the most recent
          post-effective amendment thereof) which, individually or in the
          aggregate, represent a fundamental change in the information set forth
          in the Registration Statement. Notwithstanding the foregoing, any
          increase or decrease in volume of securities offered (if the total
          dollar value of securities offered would not exceed that which was
          registered) and any deviation from the low or high end of the
          estimated maximum offering range may be reflected in the form of
          prospectus filed with the Commission pursuant to Rule 424(b) of the
          Securities Act, if, in the aggregate, the changes in volume and price
          represent no more than a 20% change in the maximum aggregate offering
          price set forth in the "Calculation of Registration Fee" table in the
          effective registration statement;

               (iii) include any material information with respect to the plan
          of distribution not previously disclosed in the registration statement
          or any material change to such information in the registration
          statement;

          provided, however, that paragraphs 9(a)(1)(i) and 9(a)(1)(ii) do not
          apply if the registration statement is on Form S-3 or Form S-8, and
          the information required to be included in a post-effective amendment
          by those paragraphs is contained in periodic reports filed by the
          registrant pursuant to section 13 or section 15(d) of the Exchange Act
          that are incorporated by reference in the registration statement.

          (2) That, for the purpose of determining any liability under the
     Securities Act, each such post-effective amendment shall be deemed to be a
     new registration statement relating to the securities offered therein, and
     the offering of such securities at that time shall be deemed to be the
     initial bona fide offering thereof.

          (3) To remove from registration by means of a post-effective amendment
     any of the securities being registered which remain unsold at the
     termination of the offering.

          (b) Subsequent Exchange Act Documents. The undersigned Registrant
hereby undertakes that, for purposes of determining any liability under the
Securities Act, each filing of the Registrant's annual report pursuant to
section 13(a) or section 15(d) of the Exchange Act (and, where applicable, each
filing of an employee benefit plan's annual report pursuant to section 15(d) of
the Exchange Act) that is incorporated by reference in the Registration
Statement shall be deemed to be a new

                                       6
registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

          (c) Indemnification. Insofar as indemnification for liabilities
arising under the Securities Act may be permitted to directors, officers and
controlling persons of the Registrant pursuant to the foregoing provisions, or
otherwise, the Registrant has been advised that in the opinion of the Commission
such indemnification is against public policy as expressed in the Securities Act
and is, therefore, unenforceable. In the event that a claim for indemnification
against such liabilities (other than the payment by the Registrant of expenses
incurred or paid by a director, officer or controlling person of the Registrant
in the successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the Registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the Securities Act and will be governed by the final
adjudication of such issue.

                                       7
Index to Exhibits
Exhibit No.                         Description of Exhibit
-----------                         ----------------------
4.1           Articles of Association of UBS AG (incorporated by reference to
              Exhibit 1.1 to the Company's Annual Report on Form 20-F for the
              fiscal year ended 31 December 2004).

4.2           Organization Regulations of UBS AG (incorporated by reference to
              Exhibit 1.2 to the Company's Annual Report on Form 20-F for the
              fiscal year ended 31 December 2004).

4.3           Instruments defining the rights of holders of long-term debt
              issued by UBS AG and its subsidiaries (incorporated by reference
              to Exhibit 2(b) to the Company's Annual Report on Form 20-F for
              the fiscal year ended 31 December 2004).

23.1          Consent of Ernst & Young Ltd.

24            Powers of Attorney.
8
SIGNATURES

          The Registrant. Pursuant to the requirements of the Securities Act of
1933, the Registrant certifies that it has reasonable grounds to believe that it
meets all of the requirements for filing on Form S-8 and has duly caused this
registration statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of Zurich, Switzerland on the 4th day of August
2005.

                                        UBS AG

                                        By: /s/ Hugo Schaub
                                            ------------------------------------
                                        Name: Hugo Schaub
                                        Title: Group Controller

                                        By: /s/ James Odell
                                            ------------------------------------
                                        Name: James Odell
                                        Title: Managing Director

          Pursuant to the requirements of the Securities Act, this registration
statement has been signed by the following persons in the capacities and on the
dates indicated.
NAME                          TITLE                    DATE
          ----                          -----                    ----
/s/ Peter Wuffli                 President of Group         04 August 2005
------------------------           Executive Board
Peter Wuffli                (principal executive officer)

/s/ Clive Standish          Group Chief Financial Officer   04 August 2005
------------------------    (principal financial officer)
Clive Standish

/s/ Hugo Schaub                   Group Controller          04 August 2005
------------------------   (principal accounting officer)
Hugo Schaub

/s/ Marcel Ospel              Chairman of the Board of      04 August 2005
------------------------              Directors
Marcel Ospel

/s/ Stephan Haeringer       Vice Chairman of the Board of   04 August 2005
------------------------              Directors
Stephan Haeringer
NAME                          TITLE                    DATE
          ----                          -----                    ----
/s/ Marco Suter             Vice Chairman of the Board of   04 August 2005
------------------------              Directors
Marco Suter

/s/ Peter Bockli             Vice Chairman and Member of    04 August 2005
------------------------         Board of Directors
Peter Bockli

/s/ Ernesto Bertarelli      Member of Board of Directors    04 August 2005
------------------------
Ernesto Bertarelli

/s/ Sir Peter Davis         Member of Board of Directors    04 August 2005
------------------------
Sir Peter Davis

/s/ Rolf A. Meyer           Member of Board of Directors    04 August 2005
------------------------
Rolf A. Meyer

/s/ Helmut Panke            Member of Board of Directors    04 August 2005
------------------------
Helmut Panke

/s/ Peter Spuhler           Member of Board of Directors    04 August 2005
------------------------
Peter Spuhler

/s/ Peter R. Voser          Member of Board of Directors    04 August 2005
------------------------
Peter R. Voser

/s/ Lawrence A. Weinbach    Member of Board of Directors    04 August 2005
------------------------
Lawrence A. Weinbach
Pursuant to the requirements of Section 6(a) of the Securities Act, as
amended, the Authorized Representative has duly caused this Registration
Statement to be signed, solely in his capacity as the duly authorized
representative of UBS AG in the United States, in the City of New York, State of
New York, on the 4th day of August 2005.

                                        By: /s/ James Odell
                                            ------------------------------------
                                        Name: James Odell
                                        Title: Managing Director