SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                                    ________

                                    FORM 6-K

                        REPORT OF FOREIGN PRIVATE ISSUER
                      PURSUANT TO RULE 13A-16 OR 15D-16 OF
                       THE SECURITIES EXCHANGE ACT OF 1934

                           For the month of July, 2005

                                   Serono S.A.
                         -------------------------------
                               (Registrant's Name)

                            15 bis, Chemin des Mines
                                 Case Postale 54
                                CH-1211 Geneva 20
                                   Switzerland
                            -------------------------
                    (Address of Principal Executive Offices)

                                     1-15096
                         -------------------------------
                              (Commission File No.)

     (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).)  ____
                                                         

     (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).)   ______

     (Indicate by check mark whether the registrant by furnishing the
    information contained in this form 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): 82-______)



                                                              [GRAPHIC OMMITTED]
                                                                          Serono
PRESS RELEASE


FOR  IMMEDIATE  RELEASE
-----------------------



              SERONO WELCOMES POSITIVE RATINGS FROM CREDIT AGENCIES

CREDIT RATINGS FROM MOODY'S AND STANDARD & POOR'S CONFIRM UNDERLYING STRENGTH
AND POSITIVE BUSINESS PROSPECTS.



GENEVA,  SWITZERLAND,  JULY  13,  2005  - Serono (virt-x:SEO and NYSE: SRA), the
third  largest  biotechnology  company in the world, today announced that it had
received  credit  ratings of A3 from Moody's and A- from Standard & Poor's, both
with  a  stable  outlook.

"These  positive  credit  ratings are an excellent reflection of our position in
the top tier of biotech companies and clearly demonstrate our low risk profile,"
comments  Stuart  Grant,  Chief Financial Officer, Serono.  "We've achieved this
result  through  our  sound financial management, the underlying strength of the
business  and  our  clear  strategic  direction  for  the  company."

According  to  both  Moody's  and Standard & Poor's, these ratings reflect their
confidence  in  the strength of Serono's solid and focussed portfolio of biotech
brands in its major therapeutic areas. The company also demonstrated good patent
protection  and limited risk from biosimilars, along with a good track record of
generating  royalty  and  licence income. Both agencies confirmed Serono's solid
cash  generation,  conservative  financial  guidelines,  and  stable  majority
shareholder  base.


                                       ###


Note  to  Editors:  Serono  will  report its Q2 results on 19 July 2005, 4.01pm,
Eastern  Time


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FOR SERONO
Some  of  the  statements  in  this  press  release  are  forward  looking. Such
statements  are inherently subject to known and unknown risks, uncertainties and
other  factors  that  may  cause  actual results, performance or achievements of
Serono  S.A.  and  affiliates  to be materially different from those expected or
anticipated  in  the  forward-looking statements. Forward-looking statements are
based on Serono's current expectations and assumptions, which may be affected by
a  number  of  factors, including those discussed in this press release and more
fully  described  in  Serono's  Annual  Report  on Form 20-F filed with the U.S.
Securities  and Exchange Commission on March 16, 2005. These factors include any
failure  or  delay  in  Serono's ability to develop new products, any failure to
receive  anticipated  regulatory  approvals,  any  problems  in  commercializing
current  products  as  a  result of competition or other factors, our ability to
obtain  reimbursement  coverage  for  our  products,  the  outcome of government
investigations and litigation and government regulations limiting our ability to
sell  our  products.  Serono has no responsibility to update the forward-looking
statements  contained  in  this press release to reflect events or circumstances
occurring  after  the  date  of  this  press  release.



ABOUT SERONO
Serono  is  a  global biotechnology leader.  The Company has eight biotechnology
products,  Rebif(R),  Gonal-f(R),  Luveris(R),  Ovidrel(R)/Ovitrelle(R),
Serostim(R),  Saizen(R),  Zorbtive(TM) and Raptiva(R).  In addition to being the
world  leader  in  reproductive  health,  Serono  has strong market positions in
neurology,  metabolism  and  growth and has recently entered the psoriasis area.
The  Company's  research programs are focused on growing these businesses and on
establishing  new  therapeutic  areas, including oncology.  Currently, there are
approximately  30  ongoing  development  projects.

In  2004,  Serono  achieved  worldwide revenues of US$2,458.1 million, and a net
income  of  US$494.2 million, making it the third largest biotech company in the
world.  Its  products  are  sold  in over 90 countries.  Bearer shares of Serono
S.A.,  the  holding  company,  are  traded  on the virt-x (SEO) and its American
Depositary  Shares  are  traded  on  the  New  York  Stock  Exchange  (SRA).


FOR  MORE  INFORMATION,  PLEASE  CONTACT:

   CORPORATE MEDIA RELATIONS:  CORPORATE INVESTOR RELATIONS:
   Tel:  +41 22 739 36 00      Tel:  +41 22 739 36 01
   Fax:  +41 22 739 30 85      Fax:  +41 22 739 30 22
   http://www.serono.com       Reuters: SEO.VX / SRA.N
   ---------------------       Bloomberg: SEO VX / SRA US

   MEDIA RELATIONS, USA:       INVESTOR RELATIONS, USA:
   Tel:  +1 781 681 2340       Tel:  +1 781 681 2552
   Fax:  +1 781 681 2935       Fax:  +1 781 681 2912
   http://www.seronousa.com
   ------------------------


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                                   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.



                                           SERONO S.A.
                                           a Swiss corporation
                                           (Registrant)



July 13, 2005                      By:     /s/ Stuart Grant
                                           --------------------------------
                                           Name:  Stuart Grant
                                           Title: Chief Financial Officer