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: June 23, 2004


         On June 23, 2004, Sanofi-Synthelabo issued the following press release.

         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.


                                     * * * *



                                                        [SANOFI~SYNTHELABO LOGO]


[GRAPHIC] INVESTOR RELATIONS


                      SANOFI-SYNTHELABO'S OFFER FOR AVENTIS
                            EXPIRATION DATE OF OFFERS

PARIS,  FRANCE--  JUNE 23,  2004-- On June 22,  2004,  the  Autorite des marches
financiers  (AMF)-- the French stock market  regulator--  announced  that it had
extended the expiration  date of  Sanofi-Synthelabo's  (PARIS:  SAN, NYSE:  SNY)
revised  offer  for the  ordinary  shares of  Aventis  (PARIS:  AVE,  FRANKFURT:
AVE.ETR, NYSE: AVE) until July 30, 2004.

Accordingly,  Sanofi-Synthelabo  confirms  that the French  offer and the German
offer will expire at 23:00 hr (Central European Summer Time), and the U.S. offer
will expire simultaneously at 5:00 p.m. (Eastern Daylight Time), on Friday, July
30, 2004.

Sanofi-Synthelabo  confirms that holders of Aventis  securities  may tender,  or
withdraw their tendered,  Aventis securities at any time until the expiration of
the offers.

As of the close of business on June 22, 2004, a total of approximately 4,990,000
Aventis ADSs had been tendered in and not withdrawn from the U.S. offer. Because
of French  centralization  procedures,  the  number of Aventis  ordinary  shares
tendered in and not  withdrawn  from the offers  cannot be known until after the
expiration of the offers.





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 Autorite des
marches  financiers  ("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 three offers will expire at the same
time.

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 as well as of the Reference  Document filed with the
AMF on April 2,  2004 (No.  04-0391)  at  www.amf-france.org  or  directly  from
Sanofi-Synthelabo on our web site at: www.sanofi-synthelabo.com.


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

INVESTOR RELATIONS DEPARTMENT
Philippe Goupit         Director of Investor Relations
Arnaud Delepine         Investor Relations Europe
Sanjay Gupta            Investor Relations US
Anne d'Halluin-Sulzer   Investor Relations


CONTACTS:
E-mail: investor-relations@sanofi-synthelabo.com
Europe                          US
Tel:   +33 1 53 77 45 45        Tel:    +1 212 551 42 93
Fax:   +33 1 53 77 42 96        Fax:    +1 212 551 49 92