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 May, 2003

                                  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-      )
                                                       ------



                                                                          SERONO



Media Release



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



            SERONO TO ACQUIRE REMAINING MINORITY INTEREST IN GENSET
                      FINAL TENDER OFFERS COMMENCED TODAY


GENEVA, SWITZERLAND - May 15, 2003 - Serono S.A. announced today that its wholly
owned subsidiary Serono France Holding S.A., which owns 96.6% of Genset S.A.,
will acquire the remaining shares of Genset that it does not already own.  Under
applicable French law, the squeeze-out of the remaining shares is a two-step
process, consisting of a repurchase tender offer followed by a mandatory
squeeze-out.

Serono France Holding today commenced two separate, related cash tender offers
as the first-step in that process.  In the United States, Serono France Holding
commenced a cash tender offer for all remaining ordinary shares of Genset S.A.
held by U.S. holders and all shares represented by American Depositary Shares of
Genset, each ADS representing one-third of a share.  Serono France Holding is
offering the U.S. dollar equivalent of EUR 8.19 in cash for each Genset share
and EUR 2.73 in cash for each one-third share represented by an ADS.  In France,
Serono France Holding commenced a cash tender offer for all remaining Genset
shares held by non-U.S. persons at the same price in euro.

There are no conditions to the offers.

On the business day following the expiration of the offers, the mandatory
second-step squeeze-out will occur and all remaining shareholders, including
those who hold shares in the form of ADSs, will have their shares automatically
converted into the right to obtain the offer price of EUR 8.19 per share or EUR
2.73 per one-third share represented by an ADS.

The U.S. tender offer and withdrawal rights are scheduled to expire at 12:00
noon, New York City time, on Friday, June 13, 2003, unless extended.  Serono
France will announce the results of the offers and the completion of the
squeeze-out when it occurs.

MacKenzie Partners Inc. is the Information Agent for the U.S. tender offer.


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ABOUT SERONO

Serono  is  a  global  biotechnology  leader.  The  Company  has six recombinant
products  on  the  market,  Gonal-F(R),  Luveris(R),  Ovidrel(R)/Ovitrelle(R),
Rebif(R),  Serostim(R) and Saizen(R) (Luveris(R) is not approved in the USA). In
addition  to  being  the  world leader in reproductive health, Serono has strong
market  positions  in  neurology,  metabolism and growth. The Company's research
programs  are  focused  on  growing  these  businesses  and  on establishing new
therapeutic  areas.  Currently,  there  are  over  30  projects  in development.

Serono  was  awarded the International James D. Watson Helix 2003 Award from the
Biotechnology  Industry  Organization  (BIO)  in  recognition  of  the Company's
outstanding  leadership  and  highest  standards  of  scientific  and  product
achievement.

In  2002,  Serono  achieved  worldwide  revenues  of US$1.546 billion, and a net
income  of  US$321  million,  making it the third largest biotech company in the
world.  The  Company operates in 45 countries, and its products are sold in over
100  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:

SERONO IN GENEVA, SWITZERLAND:
MEDIA RELATIONS:                      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: SEOZ.VX / SRA.N
---------------------                 Bloomberg: SEO VX / SRA US

SERONO, INC., ROCKLAND, MA
MEDIA RELATIONS:                      INVESTOR RELATIONS:
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)



May 15, 2003                       By:  /s/ Allan Shaw
                                        ------------------------------
                                        Name:  Allan Shaw
                                        Title: Chief Financial Officer