Filed by Sanofi-Synthelabo
                                  Pursuant to Rule 165 and Rule 425(a) under the
                                           United States Securities Act of 1933,
                                                                      as amended

                                                        Subject Company: Aventis
                                                   Commission File No. 001-10378
                                                           Date: August 13, 2004


     On August 13, 2004, at the request of the Autorite des marches  financiers,
the French  stock  market  regulator,  Sanofi-Synthelabo  caused  the  following
announcement  to be published in Les Echos, a French  financial  newspaper.  The
following is an English translation of the French  announcement,  the content of
which  Sanofi-Synthelabo  had previously included in all substantive respects in
its press release issued on August 12, 2004.

     In connection with the proposed  acquisition of Aventis,  Sanofi-Synthelabo
has filed with the United States  Securities  and Exchange  Commission  (SEC), a
registration  statement  on Form F-4 (File no:  333-112314),  which  includes  a
prospectus  and a  prospectus  supplement  relating  to the revised  offer,  and
related exchange offer  materials,  to register the  Sanofi-Synthelabo  ordinary
shares   (including    Sanofi-Synthelabo    ordinary   shares   represented   by
Sanofi-Synthelabo  ADSs) to be issued in exchange  for Aventis  ordinary  shares
held by  holders  located  in the United  States  and for  Aventis  ADSs held by
holders wherever located and has also filed with the SEC a Statement on Schedule
TO. INVESTORS AND HOLDERS OF AVENTIS SECURITIES ARE STRONGLY ADVISED TO READ THE
REGISTRATION  STATEMENT AND THE PROSPECTUS AND PROSPECTUS SUPPLEMENT RELATING TO
THE  REVISED  OFFER,  THE  STATEMENT  ON  SCHEDULE  TO,  AND ANY OTHER  RELEVANT
DOCUMENTS FILED WITH THE SEC, AS WELL AS ANY AMENDMENTS AND SUPPLEMENTS  BECAUSE
THEY CONTAIN IMPORTANT INFORMATION.  Investors and holders of Aventis securities
may obtain  free  copies of the  registration  statement,  the  prospectus,  the
prospectus  supplement  relating to the revised offer and related exchange offer
materials, and the Statement on Schedule TO, as well as other relevant documents
filed with the SEC, at the SEC's web site at www.sec.gov.  The  prospectus,  the
prospectus    supplement    relating   to   the   revised    offer   and   other
transaction-related  documents  are  being  mailed  to  Aventis  securityholders
eligible to participate in the U.S. offer and additional  copies may be obtained
for free from  MacKenzie  Partners,  Inc.,  the  information  agent for the U.S.
offer, at the following address:  105, Madison Avenue, New York, New York 10016;
telephone 1-(212) 929-5500 (call collect) or 1-(800) 322-2885  (toll-free call);
e-mail proxy@mackenziepartners.com.


                                     * * * *




                           SUBSEQUENT OFFERING PERIOD
                    IN SANOFI-SYNTHELABO'S OFFER FOR AVENTIS

Sanofi-Synthelabo  announces the success of its tender offer for the  securities
of Aventis. According to the definitive results published by the French Autorite
des marches  financiers  (AMF) in its announcement of August 12, 2004, as of the
expiration  of the offers on July 30,  2004,  in aggregate  769,920,773  Aventis
ordinary  shares had been  tendered  into the  French,  German  and U.S.  offers
(including  24,137,576  Aventis  ordinary  shares  underlying  the Aventis  ADSs
tendered into the U.S. offer). In addition, 92,692 warrants issued by Aventis in
2002 and  164,556  warrants  issued by  Aventis in 2003 were  tendered  into the
French offer.

These results indicate that 769,920,773  Aventis shares  representing  95.47% of
the  share  capital  and  95.52%  of the  voting  rights  of  Aventis,  based on
806,437,011  shares and  806,044,276  voting rights  outstanding  as of July 31,
2004, have been tendered into the offers.  After giving effect to the offers, on
a fully-diluted basis,  Sanofi-Synthelabo  will hold 89.84% of the share capital
and 89.88% of the voting rights of Aventis.

In order to allow  holders of Aventis  securities  who did not tender during the
initial offering period to benefit from the offer, and having obtained more than
two-thirds of the voting rights of Aventis, Sanofi-Synthelabo announces that, in
accordance  with  Article  5.3.2.1 of the General  Regulation  of the Conseil de
Marches  Financiers  (the  predecessor of the AMF), it is providing a subsequent
offering period of 17 trading days in the French offer, the German offer and the
U.S. offer.

The terms and conditions,  the consideration  offered and the financial analysis
of the terms of these offers are identical to those  offered  during the initial
offering   periods,   as  described  in  the  applicable   offer   documents  of
Sanofi-Synthelabo and the responsive documents filed by Aventis.

Each holder of Aventis securities will receive under the elections:

o   STANDARD ENTITLEMENT:  5 Sanofi-Synthelabo ordinary shares and (euro)115.08
    in cash for 6 Aventis  ordinary shares (or 0.8333 of a  Sanofi-Synthelabo
    ordinary share and (euro)19.18 in cash for each Aventis ordinary share);

o   ALL STOCK ELECTION: 1.1600 Sanofi-Synthelabo  ordinary shares for each
    Aventis ordinary share (or 2.3200 Sanofi-Synthelabo ADSs for each Aventis
    ADS);

o   ALL CASH ELECTION:  (euro)68.11 in cash for each Aventis ordinary share (or
    an amount in U.S. dollars equal to (euro)68.11 in cash for each Aventis
    ADS).




The proration and allocation  adjustments  described in the offer  documentation
will continue to apply to elections made with respect to Aventis ordinary shares
tendered in the subsequent  offering period.  However, as disclosed in the offer
documentation,  the results of the application of these proration and allocation
adjustments  to tenders in the  subsequent  offering  period may differ from the
results of their  application  to tenders in the initial  offering  period ended
July 30, 2004.

The subsequent  offering  periods will commence on August 13, 2004 and expire on
September 6, 2004, at 23:00 hr (Central European Summer Time) for the French and
German offers and  simultaneously  at 5:00 p.m.  (Eastern Daylight Time) for the
U.S. offer.

Sanofi-Synthelabo currently expects that the AMF will publish the results of the
subsequent  offering  periods on or about September 16, 2004.  Sanofi-Synthelabo
currently  expects that the settlement date of the subsequent  offering  periods
will occur on or about September 24, 2004.

MINORITY BUY-OUT OFFER AND COMPULSORY ACQUISITION; MERGER

At this time,  no decision  has been taken with  respect to a possible  minority
buy-out offer followed by a compulsory acquisition or with respect to a possible
merger of Aventis and Sanofi-Synthelabo.

DIVIDEND PAYMENT DATE

Under the terms of the offers, each  Sanofi-Synthelabo  ordinary share issued to
tendering  holders of Aventis ordinary shares will entitle the holders (provided
they continue to hold the Sanofi-Synthelabo  ordinary shares through payment) to
receive the dividend of (euro)1.02 that the  shareholders  of  Sanofi-Synthelabo
approved for distribution in respect of  Sanofi-Synthelabo's  2003 results. This
dividend will be paid on or about  September 30, 2004, to the holders of the new
Sanofi-Synthelabo  ordinary shares to be issued in exchange for Aventis ordinary
shares in the offers and,  assuming it is paid on September  30,  2004,  will be
paid to whoever holds those Sanofi-Synthelabo ordinary shares as of the close of
business on September 29, 2004. An interim  dividend of (euro)0.97 per share has
already been distributed on the existing  Sanofi-Synthelabo ordinary shares. The
balance of (euro)0.05  remaining on the 2003 dividend will also be paid on these
existing  Sanofi-Synthelabo  ordinary  shares on September  30, 2004, to whoever
holds  those  existing  Sanofi-Synthelabo  ordinary  shares  as of the  close of
business on September 29, 2004.

In accordance with article 7 of the COB rule no. 2002-04, this press release was
transmitted to the Autorite des marches financiers (AMF) before its publication.

IMPORTANT INFORMATION
---------------------

In connection with the proposed  acquisition of Aventis,  Sanofi-Synthelabo  has
filed a registration  statement on Form F-4 (File no.  333-112314),  including a
prospectus and a prospectus  supplement  relating to the revised offer, and will
file additional




documents with the SEC. INVESTORS ARE URGED TO READ THE REGISTRATION  STATEMENT,
INCLUDING THE PROSPECTUS AND THE PROSPECTUS  SUPPLEMENT  RELATING TO THE REVISED
OFFER,  AND ANY OTHER  RELEVANT  DOCUMENTS  FILED  WITH THE SEC,  INCLUDING  ALL
AMENDMENTS AND SUPPLEMENTS,  BECAUSE THEY CONTAIN  IMPORTANT  INFORMATION.  Free
copies of the registration  statement, as well as other relevant documents filed
with the  SEC,  may be  obtained  at the  SEC's  web  site at  www.sec.gov.  The
prospectus and the prospectus supplement relating to the revised offer and other
transaction-related  documents  are being  mailed to  Aventis  security  holders
eligible to participate in the U.S. offer and additional  copies may be obtained
for free from  MacKenzie  Partners,  Inc.,  the  information  agent for the U.S.
offer, at the following address:  105, Madison Avenue, New York, New York 10016;
telephone: 1-(212) 929-5500 (call collect) or 1-(800) 322-2885 (toll-free call);
e-mail proxy@mackenziepartners.com.

In France,  holders of Aventis  securities  are  requested,  with respect to the
offer,   to   refer   to   the   prospectus   supplement   (note   d'information
complementaire),  which has been granted visa number 04-384 by the AMF and which
is  available  on the website of the AMF  (www.amf-france.org)  and without cost
from: BNP Paribas Securities Services,  GIS-Emetteurs,  Service Logistique,  Les
Collines de l'Arche,  75450  Paris Cedex 9 and to the  recommendation  statement
(note d'information en reponse) which has been granted visa number 04-510.

The public offer to holders of Aventis  ordinary  shares located in Germany (the
"German  Offer")  is being made in  accordance  with  applicable  German law and
pursuant  to an offer  document/sales  prospectus,  which is  available  free of
charge at BNP Paribas Securities Services, Gruneburgweg 14, D-60322 Frankfurt am
Main   (Fax:   069  -  152  05  277)  and  on  the   website   of  the   Company
(www.sanofi-synthelabo.com).  Any decision to tender Aventis  ordinary shares in
exchange for  Sanofi-Synthelabo  ordinary  shares under the German Offer must be
taken  exclusively  with regard to the terms and conditions of the German Offer,
as well as with regard to the information  included in the offer  document/sales
prospectus, including any amendments thereto, issued in Germany.

The  French  Offer,  the U.S.  Offer and the  German  Offer  are  being  made on
substantially  the same terms and  completion  of these offers is subject to the
same  conditions.  It is intended that the  subsequent  offering  periods in the
three offers will expire at the same time.

This  announcement  does not  constitute an offer to purchase or exchange or the
solicitation  of an offer to sell or exchange  any  securities  of Aventis or an
offer to sell or exchange or the solicitation of an offer to buy or exchange any
securities  of  Sanofi-Synthelabo,  nor shall  there be any sale or  exchange of
securities in any jurisdiction  (including the United States, Germany, Italy and
Japan) in which such offer,  solicitation  or sale or exchange would be unlawful
prior to the registration or qualification  under the laws of such jurisdiction.
The distribution of this communication may, in some countries,  be restricted by
law or  regulation.  Accordingly,  persons  who  come  into  possession  of this
document  should  inform  themselves  of and  observe  these  restrictions.  The
solicitation  of  offers to buy  Sanofi-Synthelabo  ordinary  shares  (including
Sanofi-Synthelabo  ordinary shares represented by Sanofi-Synthelabo ADSs) in the
United  States will only be made  pursuant  to a  prospectus  and related  offer
materials  that  Sanofi-Synthelabo   expects  to  send  to  holders  of  Aventis
securities. The Sanofi-Synthelabo  ordinary shares (including  Sanofi-Synthelabo
ordinary shares represented by Sanofi-Synthelabo  ADSs) may not be sold, nor may
offers  to  buy be  accepted,  in the  United  States  prior  to  the  time  the
registration  statement  becomes  effective.  No offering of securities shall be
made  in  the  United  States  except  by  means  of a  prospectus  meeting  the
requirements  of Section  10 of the United  States  Securities  Act of 1933,  as
amended.

FORWARD-LOOKING STATEMENTS
--------------------------

This  communication  contains  forward-looking  information and statements about
Sanofi-Synthelabo, Aventis and their combined businesses after completion of the
proposed  acquisition.  Forward-looking  statements are statements  that are not
historical facts. These statements  include financial  projections and estimates
and their underlying  assumptions,  statements  regarding plans,  objectives and
expectations  with  respect to future  operations,  products and  services,  and
statements   regarding  future  performance.   Forward-looking   statements  are
generally   identified  by  the  words  "expect,"   "anticipates,"   "believes,"
"intends,"  "estimates" and similar  expressions.  Although  Sanofi-Synthelabo's
management  believes  that the  expectations  reflected in such  forward-looking
statements  are  reasonable,  investors  and holders of Aventis  securities  are
cautioned that forward-looking information and statements are subject to various
risks and  uncertainties,  many of which are  difficult to predict and generally
beyond the control of  Sanofi-Synthelabo,  that could cause  actual  results and
developments  to differ  materially  from  those  expressed  in, or  implied  or
projected by, the  forward-looking  information and statements.  These risks and
uncertainties  include those  discussed or identified in the public filings with
the SEC made by  Sanofi-Synthelabo  and  Aventis,  including  those listed under
"Cautionary Statement Concerning Forward-Looking  Statements" and "Risk Factors"
in the  prospectus/offer  to exchange included in the registration  statement on
Form F-4 that  Sanofi-Synthelabo  has filed with the SEC (File no:  333-112314).
Sanofi-Synthelabo   does  not   undertake   any   obligation   to   update   any
forward-looking  information  or  statements.  You may obtain a free copy of the
registration  statement  and  prospectus/offer  to  exchange  and  other  public
documents filed with the SEC in the manner described above.

Investors  and  security  holders  may obtain a free copy of the Form 20-F filed
with the SEC on April 2, 2004 and any other documents filed by Sanofi-Synthelabo
with the SEC at www.sec.gov and may obtain the Reference Document filed with the
AMF on April 2, 2004 (No.  04-0391)  and other  documents  filed with the AMF at
www.amf-france.org.   Free   copies   may  also  be   obtained   directly   from
Sanofi-Synthelabo  on  our  web  site  at:   www.sanofi-synthelabo.com.   or  by
telephoning 01 53 77 45 45.