EXHIBIT 5.1

                    [Letterhead of Homburger Rechtsanwalte]

                           ABB Ltd
                           Affolternstrasse 44
                           P.O. Box 8131
                           8050 Zurich








                           October 27, 2005




               ABB Ltd - Registration Statement on Form S-8 | ABB Employee Share
               Acquisition Plan


               Ladies and Gentlemen:


               We have been retained as special Swiss counsel to ABB Ltd (the
               Company) in connection with the registration on Form S-8, being
               filed with the Securities and Exchange Commission on October 27,
               2005 (the Registration Statement), and relating to the
               registration, subject to the terms and conditions of the
               conditional share capital provided for in article 4bis para. 4 of
               the Company's Articles (as defined hereinafter) (the Conditional
               Share Capital), of a maximum of 17,000,000 registered shares of
               CHF 2.50 par value of the Company (the Shares) pursuant to the
               Plan (as defined hereinafter).

               We have been requested to render an opinion in connection with
               certain matters of Swiss law.

          I.   BASIS OF OPINION

               This opinion is confined to and given on the basis of the laws of
               Switzerland in force at the date hereof and as currently applied
               by the Swiss courts. In the absence of statutory or established
               case law, we base our opinion on our independent professional
               judgment.


               This opinion is also confined to:

               (i)  the matters stated herein and is not to be read as
                    extending, by implication or otherwise, to any other matter;
                    and

               (ii) the documents listed below.

               For the purpose of giving this opinion, we have only examined
               originals or copies of the following documents:

               (i)  a copy of an electronic excerpt from the Commercial Register
                    of the Canton of Zurich dated October 24, 2005, relating to
                    the Company (the Excerpt);

               (ii) a copy of the certified articles of incorporation of the
                    Company in their version of December 9, 2003 (the Articles);

               (iii) a copy of the regulations of the board of directors of ABB
                    in their version of August, 1999 (the Regulations);

               (iv) a copy of a circular resolution of the board of directors
                    dated September 5, 2005 (the Board Resolution); and

               (v)  a copy of the "ABB Employee Share Acquisition Plan" (the
                    Plan) plan rules, issued by ABB ESAP Ltd, a company
                    established under the laws of Guernsey, (the Plan Rules).

               No documents have been reviewed by us in connection with this
               opinion other than those listed above. Accordingly, our opinion
               is limited to the above documents and their impact on the parties
               under Swiss law on the date hereof.

          II.  ASSUMPTIONS

               In rendering the opinions below, we have assumed the following:

               (a)  the Articles and the Excerpt are unchanged and correct as of
                    the date hereof and no changes have been made which should
                    have been or should be

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                    reflected in the Articles or the Excerpt as of the date
                    hereof;

               (b)  all signatures appearing on the documents reviewed by us are
                    genuine;

               (c)  the Board Resolution (i) has been adopted in accordance with
                    Swiss law, the Articles and the Regulations, (ii) accurately
                    reflects the resolutions and other matters reflected
                    therein, and (iii) has not been revoked, rescinded or
                    amended and is in full force and effect;

               (d)  all documents purporting to be copies of originals are
                    complete and conform to the originals; and

               (e)  the Plan Rules are valid, binding and enforceable under the
                    laws of England and Wales by which they are expressed to be
                    governed.

          III. OPINION

               Based on the foregoing assumptions and subject to the
               qualifications set out below, we express the following opinion:

               1.   The Company has been duly incorporated and is validly
                    existing as a corporation (Aktiengesellschaft) under the
                    laws of Switzerland.

               2.   The Conditional Share Capital has been validly created and
                    the Shares, when issued and paid for pursuant to the Plan
                    Rules, the Articles and Swiss law, will be validly issued,
                    fully paid and non-assessable.

          IV.  QUALIFICATIONS

               The above opinion is subject to the following qualifications:

               (a)  We are admitted to the Zurich bar and do not hold ourselves
                    to be experts in any laws other than the laws of
                    Switzerland. Accordingly, our opinion is confined to Swiss
                    law. We have abstained from examining any issues of any
                    other laws. In particular, and without limitation to the
                    foregoing, we do not express any opinion on the
                    admissibility or validity of, or the procedures relating to,
                    the

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                    registration of the Shares with the Securities and Exchange
                    Commission.

               (b)  This opinion relates to the laws of Switzerland in effect on
                    the date hereof. Such laws are subject to change.

               (c)  We express no opinion herein on the accuracy, correctness or
                    completeness of the Registration Statement other than as
                    expressly set forth herein above.

                                      * * *

               We hereby consent to the filing of this opinion as an exhibit to
               the Registration Statement and the inclusion of our name and
               advice attributable to us in response to Item 6 of the
               Registration Statement. In giving such consent we do not admit
               that we are in the category of persons whose consent is required
               under section 7 of the Securities Act of 1933, as amended.

               We have rendered this opinion as of the date hereof and we assume
               no obligation to advise you on changes relevant to this opinion
               that may thereafter be brought to our attention. This opinion is
               addressed to you in connection with the filing of the
               Registration Statement. It may not be used, copied, circulated or
               relied upon by any other party or for any other purpose without
               our prior written consent.

               This opinion shall be governed by and construed in accordance
               with the laws of Switzerland.

               Very sincerely yours,

               HOMBURGER RECHTSANWALTE


               /s/ Dr. Claude Lambert
               Dr. Claude Lambert

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