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 January, 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-______)



                                                                          SERONO


Media Release


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


                     SERONO COMPLETES PATIENT ENROLLMENT IN
             REBIF(R) VERSUS COPAXONE(R) COMPARATIVE CLINICAL TRIAL

  HEAD-TO-HEAD TRIAL WILL PROVIDE DATA ON THE COMPARATIVE EFFICACY AND SAFETY OF
    REBIF(R) AND COPAXONE(R) IN TREATMENT OF PATIENTS WITH MULTIPLE SCLEROSIS


GENEVA,  SWITZERLAND,  JANUARY  5,  2005  -  Serono  (virt-x: SEO and NYSE: SRA)
announced  today  that patient enrollment has been completed in a multi-national
Rebif(R)  (interferon  beta-1a)  versus  Copaxone(R)  (glatiramer  acetate)
comparative  clinical  trial.  This  two-year  trial  is designed to compare the
efficacy  of  the  two  therapies  in patients with relapsing remitting multiple
sclerosis  (RRMS),  who  were  previously  untreated  with  disease  modifying
therapies.

Over  700  patients  have  been  enrolled  and  are  being  treated  either with
Rebif(R)  44  mcg administered three times per week by subcutaneous injection or
Copaxone(R)  20  mg  administered  daily by subcutaneous injection.  The primary
outcome  of  the  trial  is  time  to first relapse.  Secondary outcomes include
assessments  of  MRI  (magnetic  resonance  imaging)  brain scans and disability
progression.  Physicians  performing  the  neurological  examinations  and
radiologists assessing the MRI scans do not know what treatment each patient has
been  allocated  to.

"We  believe  that  a head-to-head trial is necessary to provide scientific data
that can be used to compare different therapeutic options.  In the past, we have
provided  such  data, comparing Rebif(R) with Avonex(R) in the landmark EVIDENCE
trial,  which  allowed  Rebif(R)  to  gain market approval in the U.S. under the
terms  of  the  Orphan  Drug  Act,"  said Paul Lammers, Chief Medical Officer of
Serono,  Inc.  "The  ongoing  Rebif(R)  versus  Copaxone(R)  trial  will provide
comparative  data  that  will  support  an  evidence-based approach for rational
treatment  decisions  in  multiple  sclerosis, and we expect the data to support
Rebif(R) as the foundation therapy for treatment of multiple sclerosis."

Rebif(R) is the only approved MS therapy proven in a four-year clinical study in
all  three key measures of treatment effectiveness: reducing MRI lesion area and
activity(1),  reducing  relapses  and  delaying  the  progression of disability.
Rebif(R)  is the most prescribed MS disease modifying drug outside the US and is
the fastest growing one in the US.


_______________
1  The  exact  relationship  between  MRI  findings  and  the clinical status of
   patients  is  unknown.


                                                                             1/3

ABOUT  EVIDENCE

In  the  EVIDENCE  study,  Rebif(R)  was  shown to be superior over Avonex(R) in
reducing  relapses  and  MRI  measures  at  24, 48 weeks and at trial completion
(average  of  64  weeks)(1).  The  study  involved  677  patients with relapsing
remitting  multiple sclerosis (RRMS), and was designed to compare the proportion
of  patients  who  were treated with either Rebif(R) (44 mcg three times weekly,
subcutaneously)  or Avonex(R) (30 mcg once weekly, intramuscularly) who remained
relapse-free  after  24  weeks  (primary  endpoint) and 48 weeks of therapy. The
results  showed  that  patients  treated  with  Rebif(R) were significantly more
likely to remain relapse free at 24 and 48 weeks than were patients treated with
Avonex(R).  In  addition,  patients taking Rebif(R) had fewer active lesions per
MRI  scan  for  all  studied  activity  measures  and  there  was an approximate
one-third  relative  difference  in favor of Rebif(R) for measures of MRI lesion
activity.  A  comparison  of  safety based on the EVIDENCE study 48-week results
indicates that both Rebif(R) and Avonex(R) are associated with a similar overall
side  effect  profile, including flu-like symptoms, headache, fatigue and muscle
ache  that  occur in about half of the patients treated. Adverse events reported
more  frequently with Rebif(R) were injection site reactions, asymptomatic liver
function test changes and white blood cell abnormalities. Flu-like symptoms were
reported  in  significantly  more  patients  treated  with  Avonex(R)  than with
Rebif(R).


ABOUT  REBIF(R)

Rebif(R)  (interferon  beta-1a)  is  a  disease-modifying  drug  used  to  treat
relapsing  forms  of  multiple  sclerosis  and is similar to the interferon beta
protein  produced by the human body. Interferon helps modulate the body's immune
system, fight disease and reduce inflammation.

Rebif(R),  which  was  approved  in  Europe  in  1998  and in the US in 2002, is
registered  in  more than 80 countries worldwide. In the United States, Rebif(R)
is  co-marketed  by  Serono,  Inc.  and  Pfizer Inc. Rebif(R) has been proven to
reduce  MRI  lesion  activity and area(1), reduce the frequency of relapses, and
delay  the  progression  of disability. Rebif(R) is available in a 22 mcg and 44
mcg ready-to-use pre-filled syringe and can be stored at room temperature for up
to  30  days  if  a  refrigerator  is  not  available.

Most  commonly  reported  side  effects  are  injection site disorders, flu-like
symptoms,  elevation  of  liver  enzymes and blood cell abnormalities. Patients,
especially  those  with depression, seizure disorders, or liver problems, should
discuss treatment with Rebif(R) with their doctors.


ABOUT  MULTIPLE  SCLEROSIS

Multiple  sclerosis  is  a chronic, inflammatory condition of the nervous system
and  is  the  most  common, non-traumatic, neurological disease in young adults.
Multiple  sclerosis may affect approximately two million people worldwide. While
symptoms  can  vary,  the  most  common  symptoms  of multiple sclerosis include
blurred vision, numbness or tingling in the limbs and problems with strength and
coordination. The relapsing forms of multiple sclerosis are the most common.



_______________
1  The  exact  relationship  between  MRI  findings  and  the clinical status of
   patients  is  unknown.


                                                                             2/3

                                       ###

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 25, 2004. 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,  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.  Currently,  there  are  approximately 30
ongoing  development  projects.


In  2003,  Serono  achieved  worldwide revenues of US$2,018.6 million, and a net
income  of  US$390.0 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)



January 5, 2005                            By:    /s/ Stuart Grant
                                                  ------------------------
                                           Name:  Stuart Grant
                                           Title: Chief Financial Officer