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-______)



[GRAPHIC OMITTED]                                              [GRAPHIC OMITTED]
    SERONO                                                      CANCER VAX (TM)


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

              SERONO AND CANCERVAX ANNOUNCE GLOBAL DEVELOPMENT AND
                COMMERCIALIZATION COLLABORATION FOR CANVAXIN(TM)

         CANVAXIN(TM) IN PHASE 3 CLINICAL TRIALS FOR ADVANCED-STAGE MELANOMA

GENEVA,  SWITZERLAND  AND  CARLSBAD,  CALIFORNIA  -  DECEMBER  16, 2004 - Serono
(Virt-X:  SEO  and NYSE: SRA) and CancerVax Corporation (NASDAQ: CNVX) announced
today  a  worldwide  collaboration  for the development and commercialization of
Canvaxin(TM),  an  investigational  specific  active immunotherapy product being
developed  for  the  treatment of advanced-stage melanoma, a deadly form of skin
cancer.  Canvaxin(TM)  is  currently  being  evaluated  in  two  international,
multi-center Phase 3 clinical trials for the treatment of Stage III and Stage IV
melanoma.

Under  the Agreement, CancerVax and Serono will jointly develop Canvaxin(TM) for
melanoma,  as  well  as  other indications. The companies will share equally the
costs  of  developing  Canvaxin(TM)  and  seeking  regulatory  approvals  for
Canvaxin(TM).

CancerVax  and Serono will co-promote Canvaxin(TM) in the U.S. and share certain
expenses  and  profits  on a 50/50 basis. Outside the U.S., Serono will have the
exclusive  right  to  commercialize  Canvaxin(TM)  and  will  pay  royalties  to
CancerVax  based  on  its  sales  of  the  product.  Initially,  CancerVax  will
manufacture  Canvaxin(TM) for supply throughout the world. Serono may eventually
establish  a  second  manufacturing  site  for Canvaxin(TM), to supply primarily
markets  outside  the  U.S.

CancerVax  will receive an initial cash payment of $37 million, comprised of $25
million  in  upfront  signing fees and $12 million for the purchase of 1 million
shares  of CancerVax common stock. CancerVax could receive up to $253 million in
additional  payments  linked  to  the achievement of development, regulatory and
commercial  milestones.  The element of these milestone payments relating to the
receipt  of  regulatory  approvals  through  to marketing Canvaxin(TM) solely in
Stage  III  and  Stage  IV  melanoma in the U.S. and the EU could amount to $100
million.

"This  collaboration  with  CancerVax  is  a  major  milestone  in  Serono's
establishment  of  a  significant presence in the field of oncology, and further
demonstrates  Serono's  commitment  to  expanding  our  portfolio  of innovative
clinical-stage projects which address significant, unmet medical needs," Ernesto
Bertarelli,  CEO of Serono, said. "Dermatologists have a significant role in the
diagnosis  and  treatment  of melanoma in Europe and many other countries around
the  world.  The  dermatology  presence which Serono has established through the
recent  launch of Raptiva for the treatment of moderate-to-severe psoriasis will
provide  us  with  a  significant  operational  asset  on which to build for the
commercialization  of  Canvaxin(TM)."


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"We  are  very enthusiastic about establishing this collaboration with Serono to
potentially  bring  Canvaxin(TM) to patients with advanced-stage melanoma around
the  world,"  said  David F. Hale, President & CEO of CancerVax Corporation. "By
partnering  with  Serono,  a  leading  biotechnology  company  with  significant
expertise  in  the  development  and  commercialization  of biological products,
CancerVax  has  taken  a  major step forward in achieving its goal of becoming a
world  leader  in  new  therapies  for  the  treatment  of  cancer,"  said Hale.

Consistent  with  guidance  given  in  its third quarter results release, Serono
considers  the  signing of this collaboration with CancerVax to be a significant
further  business development deal, and accordingly, the impact on net income of
$27.1m  is  considered  exceptional.




ABOUT  MELANOMA

According to the American Cancer Society, melanoma is the deadliest type of skin
cancer and is the sixth most commonly diagnosed cancer in the United States.  As
reported by the World Health Organization, the worldwide incidence, or number of
newly diagnosed cases, of melanoma in 2000 was 132,600, with 37,000 people dying
of  the disease.  Furthermore, according to the National Cancer Institute, since
1997  the  incidence of new melanoma cases in the United States has increased at
an  average  rate  of more than 5% per year, one of the highest growth rates for
any  type  of  cancer.  In 2000, over 510,000 patients in the United States were
living with melanoma.  "Melanoma is one of the fastest growing types of cancers.
According  to the American Cancer Society, an estimated 55,000 new cases will be
diagnosed  in the United States in 2004, double the number from 30 years ago and
7,900 will die as a result of the disease," said Mary Loh, Executive Director of
the  American Melanoma Foundation.  "Prevention and early detection are the best
defenses  against  early-stage  melanoma,  but we desperately need new treatment
options  for  patients  suffering  with  advanced  stages  of  this  disease."




ABOUT  CANVAXIN(TM)

Canvaxin(TM),  one  of  a  new  class of products being developed in the area of
specific  active immunotherapy (SAI) or therapeutic cancer vaccines, is based on
a  proprietary  technology  that may potentially be applied to treat a number of
cancers.  Canvaxin(TM)  is  currently  being  evaluated  in  two  international,
randomized,  double-blind,  placebo-controlled  trials  designed to evaluate the
ability  of  Canvaxin(TM)  to extend the survival of patients with Stage III and
Stage  IV  melanoma  following  surgical resection of their tumors. In September
2004,  CancerVax  completed  the  planned  enrollment of 1,118 patients into its
Phase  3 clinical trial of Canvaxin(TM) for the treatment of patients with Stage
III  melanoma.  CancerVax  continues  to  make  progress  with the enrollment of
patients  in  the  Stage  IV  clinical trial and is evaluating the potential for
Canvaxin(TM)  in  the  treatment  of  other  types  of  cancer.


                                                                             2/4

ABOUT  CANCERVAX  CORPORATION  (WWW.CANCERVAX.COM)
                                -----------------

CancerVax  Corporation  is  a  biotechnology  company  focused  on the research,
development and commercialization of novel biological products for the treatment
and  control  of  cancer. The Company's lead product candidate, Canvaxin(TM), is
one  of  a  new class of products being developed in the area of specific active
immunotherapy,  also  known  as  therapeutic  cancer  vaccines.  Canvaxin(TM) is
currently  being  studied  in  two international Phase 3 clinical trials for the
treatment  of  patients with Stage III or Stage IV, or advanced-stage, melanoma.
The Company is also finalizing the design of exploratory Phase 2 clinical trials
for  patients  with  other  advanced-stage  solid  tumors.  In  addition  to
Canvaxin(TM),  CancerVax  has  licensed  three specific active immunotherapeutic
product  candidates  targeting  the  epidermal  growth factor receptor signaling
pathway,  including  SAI-EGF, which has been studied in Phase 2 clinical trials.
The  Company  plans  to identify and develop new product candidates based on its
proprietary  specific  active  immunotherapy,  anti-angiogenesis and T-oligo, or
telomere homolog oligonucleotide, technology, as well as on its human monoclonal
antibodies.  CancerVax's  corporate  headquarters  and  research and development
facility  is  located  in  Carlsbad, California, and its biologics manufacturing
facility  is  located  in  the  Los  Angeles  area.


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 Rapitva(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.  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).


FORWARD-LOOKING STATEMENTS

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 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.


                                                                             3/4

CancerVax

CancerVax  cautions  you that statements included in this press release that are
not  a  description  of  historical  facts  are  forward-looking statements. For
example,  statements about future payments under the collaboration agreement, if
any,  the manufacture of Canvaxin(TM) and plans and objectives of management are
all  forward-looking  statements.  The  inclusion  of forward-looking statements
should  not  be  regarded as a representation by CancerVax that any of its plans
will  be  achieved. Actual results may differ materially from those set forth in
this  release  due  to  the  risks  and  uncertainties  inherent  in CancerVax's
business,  including  without  limitation,  statements  about:  the progress and
timing  of  the  clinical  trials of Canvaxin(TM); the potential that results of
Phase  1  and  2  clinical  trials  of  Canvaxin(TM), which were evaluated using
retrospective  survival  analyses  that  may  be  subject to potential selection
biases,  may not be predictive of future results of the ongoing Phase 3 clinical
trials;  difficulties  or  delays in researching, developing, testing, obtaining
regulatory  approval,  producing  and marketing Canvaxin(TM); unexpected adverse
side effects or inadequate therapeutic efficacy of Canvaxin(TM) that could delay
or  prevent  product  development  or commercialization, or that could result in
recalls  or  product  liability  claims;  CancerVax's  inability  to protect its
intellectual property and proprietary technology and to maintain and enforce its
licensing  arrangements  with respect to Canvaxin(TM); the scope and validity of
patent  protection  for  Canvaxin(TM);  competition from other pharmaceutical or
biotechnology  companies;  CancerVax's  limited  experience in manufacturing and
testing  biological  products,  which  may  result  in  delayed  development  or
commercialization  of  Canvaxin(TM),  as well as lost revenue; the risk that the
collaboration  agreement  may  be terminated by Serono in certain instances; and
other  risks detailed in CancerVax's Securities and Exchange Commission filings,
including  CancerVax's  Annual  Report  on  Form  10-K for the fiscal year ended
December  31,  2003 and its Quarterly Report on Form 10-Q for the fiscal quarter
ended  September  30,  2004,  and  Serono's  Form 20-F for the fiscal year ended
December  31,  2003.  You  are  cautioned  not  to place undue reliance on these
forward-looking  statements,  which  speak  only  as  of  the  date  hereof. All
forward-looking  statements  are  qualified in their entirety by this cautionary
statement  and  CancerVax undertakes no obligation to revise or update this news
release  to  reflect events or circumstances after the date hereof. This caution
is  made  under  the safe harbor provisions of the Private Securities Litigation
Reform  Act  of  1995.

CancerVax(R) is a registered trademark of CancerVax Corporation.
Canvaxin(TM) is a trademark of CancerVax Corporation.


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


CANCERVAX CONTACT:

VINCE REARDON
CANCERVAX CORPORATION
SENIOR DIRECTOR, INVESTOR RELATIONS
760-494-4850


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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)



December 16, 2004                       By:   /s/ Francois Naef
                                             -------------------------
                                        Name:  Francois Naef
                                        Title: Secretary