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, 2005

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

                            15 bis, Chemin des Mines
                                 Case Postale 54
                                CH-1211 Geneva 20
                                   Switzerland
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                    (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).)
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     (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
---------------------


  73 PERCENT OF MODERATE-TO-SEVERE PSORIASIS PATIENTS WHO REMAINED ON CONTINUOUS
              RAPTIVA(R) THERAPY IN A 3-YEAR STUDY ACHIEVE PASI 75

  HIGH-NEED PATIENTS OF THE CLEAR-STUDY BENEFIT EQUALLY WELL FROM TREATMENT WITH
      RAPTIVA(R) AS BROADER MODERATE-TO-SEVERE PATIENT POPULATION TO ACHIEVE
        EFFICACIOUS AND WELL-TOLERATED CONTINUOUS CONTROL OF THE DISEASE

GENEVA,  SWITZERLAND  -  MAY  23,  2005  -  Serono  (virt-x:  SEO and NYSE: SRA)
announced today data from a clinical trial presented at the 3rd Spring Symposium
of  the  European  Academy  of  Dermatology  and  Venereology in Sofia, Bulgaria
showing  that  in  a  3-year  continuous  treatment  with  Raptiva(R),  73%  of
moderate-to-severe  psoriasis  patients  who  remained  on therapy for 36 months
achieved  a  75%  or  greater improvement of their Psoriasis Area Severity Index
(PASI 75). A second study, the CLEAR trial, demonstrated that high need patients
benefit  equally  well  from  treatment  with  Raptiva(R)  as  the  broader
moderate-to-severe  patient  population.

"Dermatologists  must  weigh  the  efficacy  and  safety  of different treatment
options,  in  the  long-term treatment of a chronic disease, such as psoriasis,"
said Nikolai Tsankov, Professor at the Department of Dermatology and Venereology
of  the  Sofia  School  of  Medicine,  Bulgaria.  "As Raptiva(R) has a favorable
benefit-risk profile during continuous therapy for disease control, it should be
considered  as  one  of  the  best  choice  biological  treatments  for
moderate-to-severe psoriasis, when a biological treatment is indicated."

A  3-year,  phase IIIb open-label study performed in North America evaluated the
long-term  safety  and  efficacy  of  continuous  treatment  with  Raptiva(R) in
moderate-to-severe  psoriasis  patients.  At the end of the final period of this
trial, 73% of patients (82/113) who remained on therapy demonstrated a sustained
clearing  of  psoriasis  symptoms, showing a 75% or greater improvement in their
Psoriasis  Area  Severity  Index  (PASI  75)  and  40%  of patients (45/113) who
remained  in  the  study  showed  a  90%  or greater PASI improvement (PASI 90).
Raptiva(R)  showed  a  consistent  safety  profile  during the 3-year continuous
therapy  with  no  cumulative  end-organ  toxicity  or  increased  malignancy or
infection.

A  sustained  benefit  in  continuous  treatment  with  Raptiva(R)  could  also
be confirmed  in  a  second  study.  This  multicenter,  multi-national  CLEAR 
trial  evaluated  the  safety  and  efficacy  of  Raptiva(R)  in  patients  with
moderate-to-severe  psoriasis.  The  response  of  patients  with  an  extended
treatment  with  Raptiva(R) over a 24-week period, who achieved a score between 
> PASI 50 and  PASI < 75 in  the initial 12-week treatment, continued to improve
-                   -
over  time  and nearly 50% of them (56/118) achieved a PASI 75 score by week 24.
High need patients that were not controlled by, intolerant to or contraindicated
to  at least two currently available systemic therapies responded with a similar
efficacy  and  safety  profile  to  the treatment with Raptiva(R) as the broader
moderate-to-severe patient population.


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As  demonstrated  in clinical trials, the long-term treatment with Raptiva(R) of
responding  patients with moderate-to-severe psoriasis results in an efficacious
continuous  control  of  the  disease  with  a  good  safety  profile.


ABOUT RAPTIVA(R)
Raptiva(R)  is  a  humanized  therapeutic  antibody  designed to selectively and
reversibly  block  the  activation, reactivation and trafficking of T-cells that
lead  to  the  development  of  psoriasis symptoms. Raptiva(R) is designed to be
administered once weekly via subcutaneous injection and can be self-administered
by patients at home.

Raptiva(R)  received  EU  approval  for  the  'Treatment  of adult patients with
moderate  to  severe  chronic plaque psoriasis who have failed to respond to, or
who  have  a  contraindication to, or are intolerant to other systemic therapies
including cyclosporine, methotrexate and PUVA'.

Serono  has the rights to develop and market Raptiva(R) worldwide outside of the
United  States and Japan. To date, Raptiva(R) has been launched in 17 countries,
amongst them many countries in Europe, Latin America, Asia as well as Australia.
Development and marketing rights in the United States, where Raptiva(R) has been
available  since  November  2003,  remain with Genentech Inc. (NYSE:DNA) and its
U.S. partner XOMA (Nasdaq: XOMA).

More than 3,500 patients in the U.S. and Europe have been included in Raptiva(R)
trials  to  date, creating the largest existing database of patients taking part
in studies with a biological therapy for psoriasis.


ABOUT THE 36-MONTH PHASE IIIB OPEN-LABEL STUDY
This  three-year  study  is  the  longest  study of psoriasis patients receiving
continuous  treatment  with  a  biologic  treatment. In this study, 339 patients
received  Raptiva(R) weekly for an initial 12 weeks, and patients with a PASI 50
response  or  a  static  Physician's  Global  Assessment  response  of 'mild' or
'better'  after 12 weeks of treatment were eligible to continue on a once-weekly
maintenance  dose of 1 mg/kg Raptiva(R) for 12-week periods starting at week 13.
A  total  of  290  subjects  entered  this  second  phase of the study. For each
successive  three-month  period  of  treatment, dropouts during that period were
analyzed  using  their last available PASI assessment but were excluded from the
subsequent cohorts.

Adverse  events in this study were similar to what has been observed in previous
clinical trials of Raptiva(R) and include headache, non-specific infection (e.g.
common  colds),  chills,  pain,  nausea,  weakness,  and  fever,  all  of  which
diminished  after  the  first  1  -  2  doses. Further, there was no evidence of
accumulation  or  cumulative toxicity. During the final six months of the study,
the  occurrence  of serious adverse events was low and consistent with data from
previous Raptiva(R) Phase III studies.

The  full  results  of  this study were presented at the American Association of
Dermatology ACADEMY 2005 meeting in New Orleans.

ABOUT THE CLEAR STUDY
In  this prospective, multicenter, multi-national study, a total of 793 patients
were  recruited  and randomized in a 2:1 ratio to either Raptiva(R) treatment or
placebo  for  12  weeks  (first  treatment  period).  After  12  weeks, patients
achieving  >  75% improvement in the Psoriasis Area and Severity Index (PASI 75)
           -
were  observed  either  until  they  relapsed  or  for  a  maximum  of  24 weeks
(observation  period).  Patients  then  started treatment with Raptiva(R) for 12
weeks  (re-treatment  period) and were followed for a further 8 weeks (follow-up
period).  Those  patients  who  achieved a score between > PASI 50 and PASI < 75
                                                         -                  -
after  the  initial  12  weeks  of  treatment  received Raptiva(R) for a 12-week
extended treatment (extended treatment phase). These patients were then observed
for an 8-week follow-up period.

In  all  study  periods,  the  majority  of reported adverse events were mild to
moderate in severity.


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ABOUT PSORIASIS
Psoriasis  is  a  T-cell  mediated  disease,  which  occurs when skin cells grow
abnormally,  resulting in thick, red, scaly, inflamed patches. Plaque psoriasis,
the most common form of the disease is characterized by inflamed patches of skin
("lesions")  topped with silvery white scales. Psoriasis can be limited to a few
spots  or  involve  extensive  areas of the body, appearing most commonly on the
knees, elbows, trunk, and scalp. Although it is highly visible, psoriasis is not
a  contagious  disease.  While  there  are a number of medications that may help
control the symptoms of psoriasis, there currently is no known cure.

BACKGROUND MATERIAL
For free B-roll, video and other content about Raptiva(R), psoriasis and Serono,
please  visit  the  Serono  Media  Center  www.thenewsmarket.com/Serono. You can
                                           ----------------------------
download  print-quality images and receive broadcast-standard video digitally or
by tape from this site. Registration and video is free to the media.

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).

                                       ###

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.

                                       ###

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

                            INVESTOR RELATIONS, USA:
                            Tel:  +1 781 681 2552
                            Fax:  +1 781 681 2912


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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 23, 2005                              By:  /s/ Stuart Grant
                                               --------------------------------
                                               Name:  Stuart Grant
                                               Title: Chief Financial Officer