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 December, 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                                                                  micromet


Media  Release


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

              SERONO AND MICROMET TO COLLABORATE IN DEVELOPMENT AND
                  COMMERCIALIZATION OF NOVEL ANTI-CANCER DRUG

           AGREEMENT FOR MT201, CURRENTLY IN PHASE II CLINICAL TRIALS


GENEVA, SWITZERLAND AND MUNICH, GERMANY - DECEMBER 7, 2004 - Serono (virt-x: SEO
and NYSE: SRA) and Micromet (private) have signed an exclusive collaboration and
license  agreement for the development and commercialization of Micromet's fully
human  monoclonal  antibody  MT201  (adecatumumab).  MT201  is  a  pan-carcinoma
monoclonal  antibody  directed  against  the  epithelial  cell adhesion molecule
Ep-CAM.  The  product  is  currently  being  tested  in two multicenter phase II
clinical  trials  for  the  treatment  of prostate and metastatic breast cancer.
Ep-CAM,  the  target  antigen for MT201, is overexpressed with high frequency on
most  human carcinomas, suggesting that it may have therapeutic potential in the
treatment  of a broad range of cancers, including prostate, breast, colon, lung,
stomach,  pancreatic,  head  &  neck,  and  ovarian  cancer.

Under  the  terms  of the agreement, Micromet will be responsible for completing
the  ongoing  phase  II  clinical  trials,  and  Serono  will  take over further
development  and commercialization of the product. Effective immediately, Serono
will  be responsible for all development costs. Micromet will receive an initial
license  fee  of US$10 million and additional milestone payments of up to US$138
million  if  the  product  is successfully developed and registered worldwide in
three  or  more  indications.  In  addition,  Micromet  will receive undisclosed
royalties based on net sales of the product. Under certain terms and conditions,
Micromet  may  elect  to  share  in the development and commercialization of the
product  in  the  US  and  EU  in  exchange  for  a  share  of  profits.

"With  its  longstanding  history  and experience in protein based therapeutics,
Serono  is  an  excellent  partner  for MT201," commented Christian Itin, CEO of
Micromet.  "We  are  excited  to  collaborate  with  Europe's  most  successful
biotechnology  company."

"We are committed to the development of novel targeted therapeutics for cancer,"
said  Serono's  CEO  Ernesto  Bertarelli.  "MT201  is  a  promising product with
considerable  therapeutic potential in the treatment of solid tumours. With this
important  addition  to  our  pipeline,  Serono's portfolio of novel anti-cancer
agents is evolving well." Serono is currently evaluating TACI-Ig in two clinical
trials  for  the  treatment  of  B-cell  malignancies.


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MT201 has been specifically designed to selectively eliminate tumour cells while
leaving  healthy  tissues  largely  unharmed.  Phase I data have demonstrated an
excellent  safety  profile  of  MT201, and no MT201 neutralizing antibodies have
been  observed  so far in man. An investigational new drug application (IND) for
the  product  was  recently  cleared  by  the  United  States  Food  and  Drug
Administration  (FDA)  for  the  initiation  of  phase  II studies in the United
States.

                                       ###

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.

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).

                                       ###
ABOUT  MICROMET
Micromet  AG,  a private Munich-based biotechnology company, puts novel concepts
in  immunotherapy  to  work.  Using  proprietary  technologies,  the  Company is
building  a  strong  pipeline of innovative drug candidates for the treatment of
cancer,  inflammation  and  autoimmune  disease. Two candidates are currently in
clinical  trials.  The  Company  has  established  a  powerful  drug development
platform  based  on  its  BiTE(TM)  technology ("Bispecific T cell engagers"), a
unique  drug  format  that  leverages  the  outstanding cytotoxic potential of T
cells, the most powerful 'killer cells' of the human immune system. In addition,
Micromet  is  exploiting the potential of SCAs (single-chain antibodies) for the
development  of novel drug candidates under a multi-year strategic collaboration
with  Enzon  Inc.  Micromet  has  integrated infrastructure and expertise in all
disciplines  of  drug  design  and  development.  The Company has attracted both
top-tier  life science investors and corporate drug development partners such as
MedImmune,  Inc.,  Enzon,  Inc.,  and  now  Serono.
For  further information, please visit the Company's web site at www.micromet.de


                                                                             2/3

FOR MORE INFORMATION, PLEASE CONTACT:

SERONO IN GENEVA, SWITZERLAND:

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

SERONO, INC., ROCKLAND, MA:

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


MICROMET


Media:  Evelyn  Wolf
Phone:  +49 89 895277-220
Email:  evelyn.wolf@micromet.de
        -----------------------

Investors:  Ines-Regina  Buth
Phone:  +49 89 895277-221
Email:  ines-regina.buth@micromet.de


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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 Swis  corporation
                                   (Registrant)



December  7, 2004                  By:    /s/ Francois Naef
                                          ---------------------------
                                   Name:  Francois  Naef
                                   Title: Secretary