Filed by Sanofi-Synthelabo Pursuant to Rule 135 and Rule 425(b) under the United States Securities Act of 1933, as amended, and deemed filed pursuant to Rule 14d-2(b)(2) of the United States Securities Exchange Act of 1934, as amended Subject Company: Aventis Commission File No. 001-10378 Date: February 2, 2004 ON FEBRUARY 2, 2004, THE FOLLOWING TWO ADVERTISEMENTS WERE PUBLISHED ON BEHALF OF SANOFI-SYNTHELABO IN THE FINANCIAL TIMES EUROPEAN EDITION AND THE INTERNATIONAL HERALD TRIBUNE EUROPEAN EDITION. * * * * WE REFUSE TO ACCEPT THAT SCIENTISTS DO NOT WORK TOGETHER TO SPEED UP THEIR RESEARCH. [Close-up image of old man leaning on walking stick] In an essential field such as healthcare, we must do everything possible to move faster. The coming together of Sanofi-Synthelabo and Aventis means thousands of scientists throughout the world working towards a common goal and combatting diseases more effectively. Our project will harness our complementary skills to create a leading pharmaceutical group (No.1 in Europe and No.3 worldwide) committed to improving healthcare and capable of driving strong, sustainable and profitable growth. SANOFI-SYNTHELABO'S OFFER TO AVENTIS'S SHAREHOLDERS BECAUSE HEALTH MATTERS This advertisement does not constitute an offer to sell, or an offer to purchase, any securities www.sanofi-synthelabo.com WE REFUSE TO ACCEPT THAT WE CANNOT DEVELOP MEDICINES FOR TOMORROW JUST BECAUSE OF OUR SIZE. [Image of young girl looking upward] Out of every 100,000 molecules screened only one becomes a new drug. Research is a major investment: it takes an average of 12 years and 800 million euros to obtain a medicine. That is why teaming up with Aventis will help us deliver more effective solutions to meet patients' needs. Together, we will harness our complementary skills to create a leading pharmaceutical group (No.1 in Europe and No.3 worldwide) committed to improving healthcare and capable of driving strong, sustainable and profitable growth. SANOFI-SYNTHELABO'S OFFER TO AVENTIS'S SHAREHOLDERS BECAUSE HEALTH MATTERS This advertisement does not constitute an offer to sell, or an offer to purchase, any securities www.sanofi-synthelabo.com