• Merger of equals in life sciences, first step to full merger
• Worldwide leader in pharmaceuticals and agricultural businesses with combined sales of
  US$20 billion
• Platform for sustainable growth through top-tier R&D resources, robust product pipeline,
  powerful emerging technologies and enhanced global marketing
• Management team already identified to drive new strategy and culture shift

Jürgen Dormann, Chairman of Hoechst AG, and Jean-René Fourtou, Chairman of Rhône-Poulenc SA, announced today their common intention to merge their life sciences activities into a new company, called Aventis, equally owned by Hoechst (NYSE:HOE) and Rhône-Poulenc (NYSE:RP).

Aventis will comprise the pharmaceutical and agricultural businesses of both groups. It will be incorporated in France, with global headquarters in Strasbourg. The agreement signed today launches the procedure for the first phase of a two-step plan which will eventually lead to a full merger of Hoechst and Rhône-Poulenc after the divestment of their remaining non-life sciences assets.

With 1997 pro forma sales of US$20 billion and 95,000 employees, Aventis will be a global leader in life sciences holding top positions in both pharmaceuticals and agriculture. With a combined R&D budget of almost $3 billion, it will have one of the most competitive innovation capabilities in the industry. Through the merger, Aventis will acquire one of the leading marketing and sales forces in the world.

"We want to create a new company, with European roots and global reach, to take full advantage of the extensive opportunities of life sciences in the 21st century. With its new culture, increased R&D resources, competitive position in emerging technologies, enhanced pipeline and strong
marketing muscle, Aventis will have a solid platform for sustained medium and long-term growth in both sales and profitability," said Jean-René Fourtou and Jürgen Dormann in a joint statement.

Combining the life sciences assets of both companies can be expected to provide additional operational efficiency with synergies of more than $1.2 billion over the next three years. Around 60% of the estimated savings would be in pharmaceuticals and around 40% in agriculture and other areas.

It is anticipated that Jürgen Dormann will be appointed Chairman of the Aventis Board of Management and Jean-René Fourtou Vice Chairman. The Board of Management will also include Igor Landau and Horst Waesche.

The Executive Committee of Aventis will comprise the four Board of Management members and the following senior executives: Alain Godard (Chief Executive Officer of Aventis Agriculture), Richard J. Markham (Chief Executive Officer of Aventis Pharma), Patrick Langlois (Chief Financial Officer), René Pénisson (Human Resources) and Klaus Schmieder (Chief Administrative Officer).

The closing of the transaction is anticipated for mid 1999, after completion of all legally required procedures and approvals.

Profile of Aventis: Focused on Delivering Growth

Aventis' positioning in life sciences will allow the company to take full advantage of the technological and business synergies between pharmaceuticals and agriculture. "We believe that the fields of human health, crop science and animal health operate today in a common innovation-driven environment. Aventis will have an impressive range of emerging technologies and expertise which will benefit all its businesses," said Jürgen Dormann and Jean-René Fourtou.

Aventis' 1997 pro forma consolidated sales would have amounted to $20 billion, with pharma accounting for 72% and agriculture for 28%. From a geographical breakdown standpoint, Europe would have accounted for 42%, the U.S. for 25%, Asia for 14% and the rest of the world for 19%.

Aventis' 1997 pro forma consolidated EBITDA (Earnings  Before Interest, Tax Depreciation and Amortization) would have been $3.8 billion.

Aventis Pharma: New Products and Marketing Muscle to Boost Growth Momentum

Aventis Pharma will encompass the following activities:

Prescription Pharmaceuticals -- via Hoechst Marion Roussel (HMR) and Rhône-Poulenc Rorer (RPR); 
Vaccines -- via Pasteur Mérieux Connaught; 
Biologicals -- via Centeon, which will be fully owned by Aventis and become an integral part of its core business.

Aventis Pharma will also incorporate Hoechst's 32.5% stake in the diagnostics company Dade Behring.

The combined resources and potential of these businesses will enable Aventis Pharma to build and sustain a global leadership position. Overall, Aventis Pharma will be able to exploit its increased critical mass in R&D, strong new product flow and significantly strengthened marketing
focusing on high growth products.

Robust Pipeline of New Products and Strong Innovation Potential

The pipeline of Aventis Pharma will include over 60 promising projects. The company expects a robust and balanced launch schedule over the next four years, including in particular:

Cardiovascular Disease -- cariporide, Refludan®,
Lovenox® line extensions and AMP 579;
Anti-Infectives -- Synercid® and ketolide;
Oncology -- Taxotere® line extensions, p 53 gene therapy, Flavopiridol® and oral taxoid;
Vaccines -- ImuLyme®, Hexavac® and new adult vaccine combinations;
Asthma/Allergy -- Kestine®, and Allegra®/Telfast® and Azmacort® line extensions;
Diabetes -- Insuman®, basal insulin and inhaled insulin;
Central Nervous System (CNS) -- the anti-psychotic MDL 100907 and Rilutek® for Parkinson's disease;
Biologicals -- Beriplast®, Humate®-P and anti-thrombin III;
Bone/Hormone Replacement Therapy -- Actonel® and Trimegestone®.

Aventis will possess one of the largest R&D budgets in the industry — 1997 pro forma investments of about $2.5 billion — and a wide range of emerging technologies, particularly in functional genomics, combinatorial chemistry, high-throughput screening, immunology and gene therapy. This combination of resources and expertise will provide the company with an outstanding foundation for long-term growth.

These assets will be complemented by access to a world-class network of academic and biotech alliances, particularly in the U.S., France and Germany, that Aventis Pharma intends to develop further.

Marketing Strength Focused on High Growth Products

From its creation, Aventis Pharma will be well established in a number of important core therapeutic areas. Globally, it will be world number one in Vaccines, number two in Biologicals, number three in Cardiovascular Disease and Diabetes and number four in Anti-Infectives and
Asthma/Allergy. Furthermore, in Oncology Aventis Pharma will have a fast growing franchise, driven by Taxotere® and supported by a broad pipeline across pharmaceuticals, gene therapies and anti-tumor vaccines.

Aventis Pharma will increase its worldwide competitiveness through a sharpened focus on products with excellent growth potential, and one of the leading marketing and sales forces in the  industry. These strengths will make Aventis Pharma a partner of choice for global in-licensing and
marketing deals.

The company will also benefit from being able to amortize its patent exposure over a larger sales basis.

As part of its focused strategy, Aventis Pharma will consider the disposal of its less strategic products.

Improving Position in the U.S.

Strong emphasis will be placed by Aventis Pharma on the U.S. market.

The combined distribution network will include about 3,400 sales representatives and will be further increased. These substantial marketing resources will enable Aventis Pharma to leverage fast-growing products, such as Allegra®/Telfast®, Lovenox® and Taxotere®, and capitalize
on recent and upcoming product launches including Actonel®, Arava®, cariporide, ImuLyme®, Synercid® and the anti-psychotic compound MDL 100907.

Increased funds for technology access, advertising and promotion will further contribute to building a solid foundation for future expansion.

Management

It is anticipated that Igor Landau will become Chairman of Aventis Pharma and Richard J. Markham Chief Executive Officer.

An international senior management team has already been identified. In addition to R.J. Markham, its Executive Committee will consist of the following executives:
Jean-Jacques Bertrand (Deputy to the CEO and Chairman and CEO of the Vaccines activities),
Daniel Camus (Chief Financial Officer),
Frank Douglas (Chief Technology Officer),
Bernard Dubois (Industrial Operations),
Thomas Hofstätter (Strategy and Business Development),
Peter Ladell (Special Projects),
Gerold Linzbach (Human Resources and Communications),
Philippe Peyre (Integration Office) and
Thierry Soursac (Commercial Operations).
Ruedi Waeger will remain Chief Executive Officer of Aventis Biologicals, currently named Centeon.

Aventis Agriculture: Impressive Global Leadership and Outlook

Aventis Agriculture will comprise the following activities:

CropScience, including Hoechst Schering AgrEvo and Rhône-Poulenc Agro. Hoechst and Schering have agreed in principle that Schering will join the partnership in Aventis CropScience subject to final negotiation;
Animal Nutrition, presently belonging to Rhône-Poulenc;
Animal Health, through Merial, the 50/50 joint venture between Rhône-Poulenc and Merck & Co. For the time being, it is expected that HR Vet will remain a subsidiary of Hoechst AG.

From Crop Protection to Crop Production

Significant R&D resources, a large spectrum of emerging technologies and the breadth of its product portfolio will permit Aventis CropScience to play a major role in a market rapidly evolving from crop protection to crop production — due to the combination of technologies for chemistry, plant breeding and biotechnology leading to new traits.

The strengthened resources of Aventis CropScience will allow investment in germplasm and new technologies. Combined with a network of alliances, these in-house technological resources are expected to make the company a leader in both crop protection and crop production in the medium-long term.

Broadened Product Portfolio

With total 1997 pro forma consolidated sales of $4.5 billion, Aventis CropScience will be a world leader with leadership positions in herbicides, insecticides, fungicides and non agricultural uses.

Its broadened product portfolio will provide the company with complementary weed, disease and insect management solutions through products such as LibertyLink®, BXN®, Balance®, Regent®, StarLink® and SeedLink®.

Enhancing Competitiveness in the U.S.

Through the merger, Aventis CropScience will become a market leader in Europe, Latin America and Asia-Pacific.

The top geographical priority will be the U.S. Aventis CropScience intends to substantially improve its competitiveness in this market through increased marketing strength and a large combined offer of new products for weed and insect management in corn.

The Aventis CropScience goal is to achieve a 10% market share in the U.S. Midwest in the next few years.

Strong Global Presence in Animal Health and Nutrition

Merial and Aventis Animal Nutrition are both world leaders in their respective fields of activity.

They hold strong positions in core products: antiparasitics, vaccines, vitamins and animal feed.

The future growth is based on a promising portfolio of new products such as the antiparasitic Frontline® and a wide range of pharmaceuticals and biologicals.

Management

It is anticipated that Horst Waesche will become Chairman of Aventis Agriculture and Alain Godard Chief Executive Officer.

An international Executive Committee has been identified. It will include, together with Alain Godard:
Gerhard Prante (Deputy to the CEO, Seeds and Crop Improvement Business),
Jürgen Asshauer (Chief Technology Officer),
Pascal Housset (Deputy to G. Prante, Strategy, Business Development and non-crop business),
Jean-Pierre Lac (Chief Financial Officer),
Jan Leemans (Biotechnology R&D),
Ian McManus (Supply Chain and Manufacturing),
Jan Stranges (Crop Protection Business),
Hans-Jörg Timner (Human Resources and Communications) and
Esmail Zirakparvar (Crop Protection Active Ingredients and Projects).
Christian Grenier will remain CEO of Aventis Animal Nutrition, currently named Rhône-Poulenc Animal Nutrition.

Synergies

Aventis expects to rapidly achieve synergies with a twofold aim: to ensure a high level of efficiency for the new organization and to improve its cost structure, thus enhancing its competitiveness.

The total estimated savings resulting from the merger would reach $1.2 billion within a three-year period, of which 60% would be in pharmaceuticals and 40% in agriculture and other activities.

Part of these synergies would result in job reductions. Aventis will manage the workforce transition in a socially responsible and ethical manner. Hoechst and Rhône-Poulenc are committed to put into place all necessary measures and establish an open dialogue with its employees and their representatives as soon as more precise action plans are defined.

Committed Management Team to Run a Successful Integration

The senior management team of Aventis will be fully committed to a smooth and successful integration while building the foundation for growth in the future.

Jean-René Fourtou and Jürgen Dormann said: "Our shared vision and common approach to business are key to ensuring the successful integration. Aventis intends to adopt the best industry practices of its two parents in order to build a modern, creative and competitive company, with efficient processes and lean infrastructures, able to retain, attract and reward the best employees."

"Our priority — added Jean-René Fourtou and Jürgen Dormann — will be to maintain business momentum in the coming months and, at the same time, make sure that the integration will be carried out rapidly and smoothly. We will personally steer this process." Klaus Schmieder will be
responsible for the management of this process at the Executive Committee level.

Corporate Governance

The corporate governance structures of Aventis and its two parent companies will be aligned in preparation of the full merger of Hoechst and Rhône-Poulenc, which is expected to occur within the next two to three years.

A ten-member Supervisory Board for Aventis would be created. It is anticipated that Marc Viénot would be designated as Chairman and Martin Frühauf as Vice-Chairman. The ten members of this Supervisory Board will at the same time be members of Rhône-Poulenc's future Conseil d'Administration and constitute the future shareholder representation in the Supervisory Board of
Hoechst AG.

The four members of Aventis' Board of Management will sit on both Rhône-Poulenc's Conseil d'Administration and Hoechst's Management Board, which will also include Klaus Schmieder. He will be in charge of Hoechst's business activities not contributed to Aventis.

Terms of the Transaction

Aventis will be 50/50 owned by Hoechst and Rhône-Poulenc respectively, both of which will continue to be publicly listed following the completion of the transaction and will be renamed Aventis Hoechst and Aventis Rhône-Poulenc.

Hoechst Marion Roussel, Rhône-Poulenc Rorer, Pasteur Mérieux Connaught, Centeon, AgrEvo, Rhône-Poulenc Agro, Rhône-Poulenc Animal Nutrition and the 50% Rhône-Poulenc stake in Merial would be contributed in the new legal entity, as well as the 32.5% participation of Hoechst in Dade Behring.

The creation of Aventis will not involve either exchanges or acquisitions of shares at the parent company level and will not lead to new additional debt.

Aventis would be a French-incorporated company and apply accounting principles that comply with French law and that are generally accepted in the United States for consolidated financial statements (U.S. GAAP). Aventis' accounts would be reported in Euros. The transaction will be accounted for using purchase accounting method.

Divestment of Non-Core Businesses

In preparation of the envisioned full merger, Hoechst and Rhône-Poulenc intend to pursue the timely divestment of their remaining chemical businesses, in line with the strategy they have both already started to implement.

Earlier this year, Rhône-Poulenc floated a minority equity stake in its chemicals business, Rhodia. In October 1998, Hoechst announced the definitive agreement to sell Herberts and, on November 17, it announced plans to demerge Celanese and Ticona into an independent, publicly
traded company to be known as Celanese AG.

Timetable

The merger is expected to be submitted to both Rhône-Poulenc's and Hoechst's General Shareholder Meetings by mid 1999, after the regulatory approvals have been obtained and the legal procedures carried out.

The Lazard Houses served as financial advisor for Hoechst. Goldman Sachs International and Rothschild & Cie. served as financial advisors for Rhône-Poulenc.

Forward-looking statements in this release are made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Although the Company believes the expectations contained in such forward-looking statements are reasonable, it can give no such assurance that such expectations will prove to be correct.

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