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 October, 2004

                                  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
---------------------


FOUR YEAR DATA SHOWS 54% REDUCTION IN RELAPSE RATE AND 76% OF MS PATIENTS REMAIN
                    FREE OF DISEASE PROGRESSION WITH REBIF(R)

      SUSTAINED EFFICACY OF REBIF(R) FURTHER DEMONSTRATED IN LONG TERM DATA
            FROM PRISMS STUDY PRESENTED AT THE 20TH ECTRIMS CONGRESS


SERONO  (VIRT-X: SEO AND NYSE: SRA) -VIENNA, AUSTRIA, OCTOBER 8, 2004 - Patients
with  relapsing-remitting multiple sclerosis (RRMS) who were on placebo and then
treated  with  Rebif(R) in the PRISMS study showed substantial clinical benefits
with  a  54%  relative  reduction  in relapse rate, Serono announced at the 20th
congress  of  the  European  Committee  for  Treatment  and Research In Multiple
Sclerosis  (ECTRIMS)  meeting  in  Vienna,  Austria.

The  data  also  showed  a  significant  improvement in MRI results for patients
treated  with  Rebif(R)  44  mcg.  There was a highly, statistically significant
relative  reduction in the mean number of brain lesions(1) of 67%.  In addition,
76%  of  patients  treated  with  Rebif(R)  44  mcg  remained  free  of  disease
progression.

"Our  results  show  the  immediate  and  long-term  benefits  of treatment with
Rebif(R)  in  controlling  MS,"  said Dr Paul Lammers, Head of Neurology Product
Development  at  Serono.  "This is important news for patients with MS, as these
data  further  demonstrate  that  treatment  with  high-dose,  high-frequency
interferon beta-1a can slow disease progression and enable people with relapsing
MS  to  have  an  active  life  longer."

This  data  is  based  on  a prospective pre-planned analysis of the progress of
patients  who  received  two  years  of placebo therapy followed by two years of
Rebif(R)  in  the  PRISMS  study.  The  four  year  PRISMS  study  demonstrated
significant improvements in the three key efficacy measures of MS: reductions in
MRI  lesion  area  and  activity(2), reduced frequency of  relapses, and delayed
disability  progression. Rebif(R) is the only disease-modifying drug with proven
efficacy  in  all  three  measures.

The  most  frequently  reported  adverse  events  were  flu-like  symptoms  and
injection-site  reactions, the majority of which were mild. No new safety issues
were  noted.

These  results  are  consistent with the PRISMS long-term follow up study, which
showed  that  patients who started on high-dose and high-frequency Rebif(R) from
the start did the best in terms of disease progression over eight years.


_______________________________
(1)  Number of T2 active lesions per patient per scan

(2)  The  exact  relationship  between  MRI  findings and the clinical status of
     patients  is  unknown


                                                                             1/3

ABOUT THE PRISMS STUDY

The  placebo-crossover  data  come  from  the  PRISMS  study,  a  double  blind,
placebo-controlled  study,  which  began in 1994, and involved 560 patients with
RRMS  at  22  centers  in  9  countries.  Patients were originally randomized to
receive  Rebif(R)  44  mcg  sc  tiw  (184 patients), Rebif(R) 22 mcg sc tiw (189
patients) or placebo (187 patients). After the first two years, patients who had
received placebo were then re-randomized to receive the active drug at a dose of
22  mcg  or  44  mcg sc tiw; all patients were followed for a further two years.
For the placebo-crossover analysis presented today at the 20th ECTRIMS Congress,
only placebo patients with data in both years 1-2 and years 3-4 (n=172/187) were
included for analyses in order to permit within-patient comparisons.

The  two-year results from the PRISMS study showed that both doses of interferon
beta-1a  significantly  reduced MRI activity and area, relapse rates, as well as
reduced  progression  of  Expanded  Disability  Status  Scale  (EDSS)  scores.
Dose-blinded  extension  data  to  four  years  demonstrated sustained treatment
benefit  over  time,  with  increasing  evidence  of  a dose-effect that favored
Rebif(R) 44 mcg. The Long-Term Follow Up (LTFU) assessment was then performed on
the seventh or eighth anniversary of patients' enrollment in the original PRISMS
study,  and  these  data  provided  a  comprehensive  long-term clinical and MRI
assessment of cohort of MS patients on therapy with interferon. The LTFU results
support the long-term effectiveness of Rebif(R) 44 mcg in the treatment of RRMS.


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(3), 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.



_______________________________
(3)  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) (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 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 2486           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)



October 8, 2004                    By:    /s/  Francois Naef
                                          -----------------------------------
                                   Name:  Francois Naef
                                   Title: Secretary