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                                    FORM 6-K
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                            Report of Foreign Issuer

                      Pursuant to Rule 13a-16 or 15d-16 of
                       the Securities Exchange Act of 1934

                        For the month of September, 2005

                        Commission File Number: 333-07654


                                  ENDESA, S.A.
                 (Translation of Registrant's Name into English)

                              Ribera del Loira, 60
                               28042 Madrid, Spain
                     (Address of principal executive office)

        Indicate by check mark whether the registrant files or will file
             annual reports under cover of Form 20-F or Form 40-F:
                Form 20-F   X            Form 40-F
                          -----                    -----

       Indicate by check mark if the registrant is submitting the Form 6-K
            in paper as permitted by Regulation S-T Rule 101(b)(1):
                     Yes                        No   X
                          -----                    -----
       Indicate by check mark if the registrant is submitting the Form 6-K
            in paper as permitted by Regulation S-T Rule 101(b)(7):
                     Yes                        No   X
                          -----                    -----

    Indicate by check mark whether by furnishing the information contained
in this Form, the Registrant is also thereby furnishing the information to the
Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934:
                     Yes                        No   X
                          -----                    -----

  If "Yes" is marked, indicate below the file number assigned to the registrant
                     in connection with Rule 12g3-2(b): N/A
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                                                     Madrid, 12th September 2005



Dear                   ,

I am writing to update you on  Endesa's  response to the  hostile  tender  offer
launched by Gas Natural  (the  "Offer") and inform you of what to expect from us
in the coming weeks.

As you will have  seen,  Endesa's  Board of  Directors  has  rejected  the offer
unanimously based on the conviction that it is grossly inadequate and not in the
best interests of our  shareholders.  We strongly believe  Endesa's  stand-alone
Strategic Plan will deliver superior value to our  shareholders  compared to the
(highly  uncertain) value implied by the Offer.  Furthermore,  Endesa's Board of
Directors is confident of achieving this superior value without the  significant
risk entailed by the proposed transaction.

We are  currently  preparing  a  comprehensive  response  to the  offer and will
contact you shortly to schedule a time to discuss it in person. In the meantime,
we ask for your continued support and confidence in the strong positive momentum
of the Endesa story.

Yours sincerely,





Rafael Miranda
CEO



                                   SIGNATURES

Pursuant  to the  requirements  of the  Securities  Exchange  Act of  1934,  the
registrant  has duly  caused  this  report  to be  signed  on its  behalf by the
undersigned, thereunto duly authorized.

                                        ENDESA, S.A.

Dated: September 14th, 2005                  By: /s/ Alvaro Perez de Lema
                                                 --------------------------
                              Name: Alvaro Perez de Lema
                              Title: Manager of North America Investor Relations