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
                    ----------------------------------------
                    (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                                                                 NOVIMMUNE


Media Release

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

               SERONO AND NOVIMMUNE TO COLLABORATE IN DEVELOPMENT
                 OF TWO NOVEL TREATMENTS FOR AUTOIMMUNE DISEASES

GENEVA,  SWITZERLAND  -  MAY  17,  2005 - Serono (virt-x: SEO and NYSE: SRA) and
NovImmune (private) have signed an exclusive agreement under which NovImmune has
granted  Serono  exclusive  worldwide rights to develop and commercialize two of
NovImmune's  fully  human  monoclonal antibodies, NI-0401 and NI-0501, which may
have  therapeutic  potential  in  a  broad  range  of  autoimmune  diseases:

-    NI-0401  targets  the  CD3  antigen,  a  key regulator in the activation of
     T-cells.  The  proliferation  of  activated  T-cells  is a hallmark of many
     autoimmune diseases, including insulin-dependent diabetes, Crohn's disease,
     multiple  sclerosis  and  rheumatoid  arthritis,  and  of  organ transplant
     rejection.
-    NI-0501 targets interferon-gamma, a key cytokine involved in the regulation
     of  immune  and  inflammatory  responses.  Interferon-gamma  is
     overexpressed  in autoimmune diseases such as systemic lupus erythematosus,
     Crohn's disease and several forms of vasculitis.

NI-0401  and  NI-0501  are  currently  in  preclinical  development.  NI-0401 is
expected  to  enter  clinical  trials  later  this  year.

Under  the  terms of the agreement, NovImmune is responsible for the development
of  the  two  products  until the completion of Phase IIa clinical trials, after
which  Serono  will take over further development. Serono will pay a license fee
of  $5 million for the two products, make a CHF 7.5 million equity investment in
NovImmune,  and lend NovImmune up to CHF 7.5 million, convertible into shares of
NovImmune  on certain conditions or repayable with accrued interest at maturity.
Based  on  the  successful development and initial registration of the products,
NovImmune  may  receive  up  to  $  105 million in future milestone payments. In
addition,  NovImmune may receive further milestone payments based on approval of
the  products  for  additional indications, and will also be entitled to receive
undisclosed  royalties  based  on  eventual  net  sales  of  the  products.

"NovImmune  is  proud  of  this  alliance  as it represents a recognition of the
quality  and  clinical relevance of these products. Our products can profit from
Serono's  expertise  in development and marketing across multiple indications to
maximize  their  full  potential"  declared  Jack Barbut, NovImmune's CEO. "More
specifically,  NI-0401, which should enter the clinic later this year, addresses
a  basic  mechanism  of the immune response and could be efficacious in treating
numerous  different  immune  related  diseases."

"NovImmune has used state-of-the-art technologies to design antibodies with very
distinctive  properties," said Tim Wells, Head of Research at Serono. "We expect
that  NI-0401  and  NI-0501  will  have  significant  advantages  over precedent
molecules  and  that  those  advantages  will translate into greater therapeutic
potential  for  the  treatment  of  chronic  autoimmune  disorders."


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                                       ###

FOR  SERONO
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.

                                       ###

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).

ABOUT  NOVIMMUNE
NovImmune  is  a  Geneva-based  product  development  company focusing on immune
mechanisms  in  order to clinically impact Immune Related Diseases, Inflammation
and Organ transplantation. NovImmune develops fully human monoclonal antibodies,
based  on  its  direct  access  to  both the transgenic mouse lines and antibody
display  technology.  NovImmune  has  a strategic partnership for GMP production
with  Lonza  Biologics.  In  addition,  NovImmune  is  developing a new class of
immunosuppressors  and  anti-inflammatory  agents  as  low  molecular  weight
inhibitors  of  MHC  Class  II  expression, directed against highly specific and
totally validated protein targets. NovImmune's first product NI-0401 is expected
to  enter  clinical  trials  in  Q4  2005.

FOR MORE INFORMATION, PLEASE CONTACT:

SERONO
  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
  ------------------------

NOVIMMUNE SA
  :
  Tel:  +41 22 839 41 01
  Fax:  +41 22 839 41 02
  http://www.novimmune.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 17, 2005                         By:  /s/ Stuart Grant
                                          ------------------------------
                                          Name:  Stuart Grant
                                          Title: Chief Financial Officer