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                                                                    PFIZER


MEDIA RELEASE

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


    REBIF(R) LABELING CHANGES REFLECT EFFICACY AND CONVENIENCE OF THE FASTEST
                        GROWING MS TREATMENT IN THE U.S.

  UPDATED LABEL SAYS PATIENTS TREATED WITH REBIF(R) ARE MORE LIKELY TO REMAIN
                        RELAPSE FREE AT 24 AND 48 WEEKS
                      VS. PATIENTS TREATED WITH AVONEX(R)


ROCKLAND,  MA,  AND  NEW  YORK,  NY, MAY 22, 2003 - Serono, Inc. and Pfizer Inc,
co-promoters  of  Rebif(R)  (interferon beta-1a) in the US, announced today that
the U.S. Food and Drug Administration (FDA) has approved additional efficacy and
product  stability  information  for Rebif(R). The new label changes reflect the
treatment's efficacy and convenience in treating multiple sclerosis.

The  new  labeling  changes include an update to the Clinical Studies section to
add 48-week data from the EVIDENCE study(1). This head-to-head study of Rebif(R)
and  Avonex(R)  (interferon  beta-1a)  compared  the  proportion  of MS patients
treated with Rebif(R) or Avonex(R) who were relapse free after 24 weeks (primary
end  point)  and  48 weeks. The label expansion will now reflect that, "Patients
treated  with  Rebif(R) 44 mcg sc tiw were more likely to remain relapse free at
24  and  48  weeks  than  were  patients  treated  with Avonex(R) 30 mcg im qw."

"Serono  and Pfizer are pleased with the FDA's approval of the new label changes
for  Rebif(R).  The  label  expansion  reflects  additional  scientific  data
demonstrating  Rebif(R)'s  clinical  superiority  over  Avonex(R)  at  reducing
frequency  of relapses in patients with relapsing remitting MS at both 24 and 48
weeks,"  said  Gordon  Francis,  M.D.,  Vice  President,  Neurology  Clinical
Development  Unit,  Serono,  Inc.

Furthermore,  the  FDA also approved label changes related to Rebif(R) temporary
storage  at  room  temperature.  This change enhances Rebif(R)'s ease-of-use for
people  who  are  currently  taking  the  therapy  to  treat their MS. The label
expansion will include that, "Rebif(R) may be stored at or below 25 degrees C/77
degrees  F  for up to 30 days and away from heat or light" and will be reflected
in  the  Stability  and

_______________________________
(1)  Panitch  H,  Goodin  DS, Francis G, et al. Randomized, comparative study of
interferon  beta-1a  treatment  regimens  in  MS:  The  EVIDENCE  (Evidence  for
Interferon  Dose-response  European-North  American Comparative Efficacy) Trial.
Neurology  2002;  59:  1496-1506.



Storage  section.  The  same  room  temperature  storage conditions were already
allowed  in  the  other  countries  where  Rebif  is  approved.

"With  Rebif(R)'s  temporary  room  temperature labeling, we are building on our
commitment  to  offer  consumers not only a highly efficacious MS treatment, but
also  the  added  convenience that patients seek," said Deborah Brown, Executive
Vice  President,  Neurology,  Serono,  Inc.

Christy  Demory,  an  attorney from North Carolina, who takes Rebif(R), welcomed
the  change.  "Between family and work, I am always on the go and sometimes need
to  carry  Rebif(R)  with  me  to  my office or on an overnight outing or when I
travel,  so  it's  great  to  have  the  flexibility  of  leaving it out at room
temperature,"  she  said.  "It's  one  less  thing  I  have  to  think  about."

A  revised  patient  Medication  Guide  will also be available that reflects new
storage  and  needle  disposal  information.

48-WEEK  EVIDENCE  DATA  SUMMARIZED
The  expanded  Rebif(R)  label  now contains data from the head-to-head EVIDENCE
study  of  677  patients  with  relapsing  remitting  MS. The study compared the
proportion  of  MS  patients  treated with either Rebif(R) or Avonex(R) who were
relapse-free  after  24  weeks  (primary endpoint) and 48 weeks. The data showed
that  75% of patients who received Rebif(R) (44 mcg administered subcutaneously,
three  times weekly) did not have a relapse after 24 weeks of treatment compared
to  63% of patients treated with Avonex(R) (30 mcg administered intramuscularly,
once weekly) (p<0.001). The improvement was sustained at 48 weeks at which point
62%  of  Rebif(R)  patients  were  relapse  free as compared to 52% of Avonex(R)
patients  (p=0.009).

Magnetic  Resource  Imaging  (MRI) was used to assess brain lesions periodically
throughout  the  48-week  study. Patients treated with Rebif(R) had fewer active
lesions  per  MRI  scan  for  all activity measures with effects seen within 2-3
months  of  starting  treatment.  There  was  an  approximate one-third relative
difference  in  favor  of Rebif(R) and treatment effects were maintained over 48
weeks  for  measures  of  lesion  activity.  The  exact relationship between MRI
findings  and  clinical  outcomes  for  patients  is  unknown.

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,  fights  disease  and  reduces  inflammation.

Rebif(R)  has  been  proven  to  slow  the course of relapsing forms of multiple
sclerosis.  In clinical studies, Rebif(R) 44 mcg administered three times a week
by  subcutaneous  injection has been shown to slow progression of disability and
reduce the frequency of relapses in relapsing-remitting MS. Additionally, use of
Rebif(R)  was  shown  to statistically significantly reduce the number of active
brain



lesions  and  T2  lesion area as measured on MRI. The exact relationship between
MRI  findings  and  clinical  status  of  patients  is  unknown.

People  living  in  the  US with relapsing forms of MS can find more information
about  Rebif(R)  in  the  full  prescribing  information,  online  at
www.mslifelines.com  or  by  calling MS LifeLines(TM) at 1-877-44REBIF. Patients
-------------------
should be instructed to read the Medication Guide accompanying the product. Most
commonly  reported side effects are injection site disorders, flu-like symptoms,
elevation  of liver enzymes and blood cell abnormalities. Compared to Avonex(R),
adverse  reactions  were similar - despite Rebif(R) being administered at higher
and  more  frequent  doses(2).  Exceptions  included  injection  site disorders,
hepatic  function  disorders, white blood cell abnormalities, abdominal pain and
depression,  which  were more frequent with Rebif(R). Patients, especially those
with depression, seizure disorders, or liver problems, should discuss with their
doctors  whether  Rebif(R)  is  right  for  them.


ABOUT  SERONO
Serono,  Inc.,  located  in Rockland, MA, is the US affiliate of Serono, S.A., a
global  biotechnology  leader, headquartered in Geneva, Switzerland. The Company
has  six  recombinant  products on the worldwide market: Gonal-F(R) (follitropin
alfa  for  injection),  Luveris(R)  (lutropin  alfa),  Ovidrel(R)/Ovitrelle(R)
(choriogonadotropin  alfa  for  injection),  Rebif(R)  (interferon  beta-1a),
Serostim(R)  [somatropin  (rDNA origin) for injection] and Saizen(R) [somatropin
(rDNA  origin)  for  injection].  (Luveris(R)  is  not  approved  in the US.) 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  is  committed  to  helping  people  living  with  MS  as  well as the MS
community. The Company has conducted leading research and product development in
the area of multiple sclerosis and other diseases. Serono's growing portfolio of
MS  products  is  used  to  treat  both  relapsing forms of MS and worsening MS.

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 $1.546 billion, and a net income
of  $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).

ABOUT  PFIZER
Pfizer  Inc  discovers,  develops, manufactures and markets leading prescription
medicines,  for  humans and animals, and many of the world's best-known consumer
products.



_______________________________
(2)  Data on file. Amendment to BLA File, Study 21125. Serono, Inc.; 2002.



                                       ###


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 April 17, 2003. 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.


FOR MORE INFORMATION, PLEASE CONTACT:


  MEDIA RELATIONS           MEDIA RELATIONS
  SERONO, INC.              PFIZER INC.
  ROCKLAND, MA              NEW YORK, NY
  Tel: 781-681-2340         Tel: 212-733-4889
  Fax: 781-681-2935         Fax: 212-808-8799
  www.seronousa.com         www.pfizer.com
  -----------------         --------------



                                   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 22, 2003                          By:  /s/  Allan Shaw
                                           ---------------------------
                                           Name:  Allan Shaw
                                           Title: Chief Financial Officer