Hoechst and Rhone-Poulenc announced today that they have agreed upon the planned accelerated, full merger of both companies into Aventis by November 1999. On Tuesday, May 11, the Supervisory Board of Hoechst and the Conseil d'Administration of Rhône-Poulenc approved
the transaction. Kuwait Petroleum Corporation (KPC), the largest shareholder of Hoechst AG, also approved the planned merger in principle.

As announced on December 1, 1998, Aventis will be a French incorporated company, headquartered in Strasbourg. A balanced corporate governance and senior management structure will be implemented. Jürgen Dormann will act as Chairman of the Board of Management and Jean-René Fourtou as Vice-Chairman.

Hoechst and Rhône-Poulenc plan to submit this project to extraordinary shareholder meetings in mid-July 1999.

Prior to the merger, Hoechst intends to:
* demerge selected chemical assets into Celanese AG
* distribute a special dividend to its shareholders
* repurchase a portion of its shares.
An exchange offer will be launched by Rhône-Poulenc for all Hoechst's outstanding shares in October 1999, pending regulatory clearances and completion of all legal and fiscal procedures. Aventis will be a publicly traded company, listed in Paris, Frankfurt and New York.

"We will achieve our goal much earlier than initially planned: the full merger into Aventis as a publicly quoted life sciences company", said Jürgen Dormann, CEO of Hoechst AG, and Jean-René Fourtou, Chairman and CEO of Rhône-Poulenc S.A. "This is a major step forward for Aventis and all its shareholders".

Terms of the Transaction
The transaction will be realized through an exchange offer by Rhône-Poulenc - which will be renamed Aventis - for all the outstanding shares of Hoechst.
This offer will be launched in October.

Prior to this exchange offer, Hoechst will take the following steps:

* The demerger of a substantial part of its industrial businesses announced at the end of 1998 will be expanded to include additional activities. The shares of Celanese AG, a publicly quoted company, will be distributed to Hoechst's shareholders in a ratio of 1 for 10. The company
will have net corporate debt of EUR 1 billion - less than originally planned.

* The shareholders of Hoechst will receive a special dividend amounting to EUR 1.5 billion. Eligible shareholders will also receive the full corporation tax credit. The payment of the special dividend to Hoechst shareholders is conditional upon the successful implementation of the
Aventis transaction.

* Between mid-May and early October, Hoechst will seek to repurchase around 29 million of its own shares, equivalent to approximately 5% of the subscribed capital.

Taking all these transactions into account, the exchange ratio for the tender offer has been set at 3 Rhône-Poulenc shares for 4 shares of Hoechst.

"Hoechst AG shareholders will thus receive a 53 percent stake in the new, publicly quoted life sciences company Aventis, one share of Celanese AG for every ten Hoechst shares they own, and a special dividend," is how Jürgen Dormann summarized the multistage transaction.

Assuming Hoechst's repurchase of 29 million shares prior to the exchange offer and 100% acceptance of this offer, the pro forma ownership of Aventis would be 47% and 53% for Rhône-Poulenc and Hoechst shareholders, respectively. To succeed, the minimum acceptance rate for the exchange offer has to be 90 percent.

Expected Timetable
Hoechst AG shareholders will be asked to approve the demerger of Celanese AG and the merger with Rhône-Poulenc at an extraordinary shareholders' meeting in mid-July 1999. In addition, shareholders will be asked to approve a short fiscal year ending on July 31, 1999 in order to create the preconditions for the payment of a special dividend. The invitation to this shareholders'
meeting, which will contain detailed information on both transactions, will be published and sent out to shareholders in early June.

Rhône-Poulenc S.A. will ask its shareholders to approve the merger into Aventis at an extraordinary general meeting in mid-July 1999.

Hoechst AG will hold an annual general meeting in October to decide on the payment of a special dividend.

Rhône-Poulenc will hold an extraordinary shareholders' meeting in November to approve the issuance of Rhône-Poulenc shares.

The closing of the full merger between Hoechst and Rhône-Poulenc into Aventis is expected to take place in November 1999.

Aventis: Focus on Life Sciences
Following the completion of the exchange offer, Rhône-Poulenc will be renamed Aventis.

In line with the strategy announced on December 1, 1998, Aventis will fully focus on life sciences and plans to implement the divestiture of all remaining chemical businesses.

Aventis will include the following main businesses of Rhône-Poulenc and Hoechst:

Pharmaceuticals:
Hoechst Marion Roussel, Rhône-Poulenc Rorer, Pasteur Mérieux Connaught, 50% of Pasteur Mérieux-Merck Sharp Dohme (joint venture with Merck & Co.), Centeon, Hoechst's interest in Dade Behring.

Agriculture:
Rhône-Poulenc Agro, Hoechst Schering AgrEvo, Rhône-Poulenc Animal Nutrition, 50% of Merial (joint venture with Merck & Co.).

Chemicals and other:
Following the Celanese demerger, Aventis will own: assets to be divested the animal health company Hoechst Roussel Vet, interests in Messer (66.7%) and Wacker-Chemie (50%) as well as a 45% share in Clariant and a 68% share in Rhodia, both publicly listed specialty chemical companies.

Organization and Corporate Governance
Aventis will have a two-tier board structure, comprising a Supervisory Board and a Board of Management.

Together with Jürgen Dormann, Chairman, and Jean-René Fourtou, Vice-Chairman, the Board of Management will include Igor Landau and Horst Waesche.
It is anticipated that Marc Viénot will be named Chairman of the Supervisory Board and Martin Frühauf Vice-Chairman. The other members will be equally designated by Rhône-Poulenc and Hoechst.
The designated Executive Committee of Aventis will be identical to the one announced on December 1, 1998. It will comprise the four members of the Board of Management and the following senior executives: Richard J. Markham (Chief Executive Officer of Aventis Pharma), Alain Godard (Chief Executive Officer of Aventis Agriculture), Patrick Langlois (Chief Financial
Officer), René Pénisson (Human Resources) and Klaus Schmieder (Chief Administrative Officer).

Aventis corporate headquarters will be in Strasbourg, France. The headquarters of Aventis Pharma will be in Frankfurt, Germany and that of Aventis Agriculture in Lyon, France.

Since January 1999, the preparations for the integration of Aventis have been proceeding in a very positive spirit of cooperation. More than 600 individuals have been designated for senior management positions in the new company. Management will ensure that this momentum is sustained so that on closing Aventis will be positioned to immediately realize its life sciences
vision.

Demerger of Celanese AG including most of the industrial activities In November 1998, Hoechst announced plans to demerge the Group companies Celanese (organic basic chemicals) and Ticona (technical polymers), as well as a number of other industrial and service firms into a new
publicly quoted entity to be called Celanese AG. Now the companies Nutrinova (food ingredients) and Trespaphan (polypropylene films) as well as Hoechst interests in the joint ventures Targor (50%) - the polypropylene joint venture with BASF - and Dyneon (46%) - the fluoropolymers joint
venture with 3M - will also become part of Celanese AG. The inclusion of these businesses will augment the portfolio of Celanese AG and help speed up the implementation of the Group strategy.

The new company will have around 16,000 employees, 4,100 of whom will be in Germany. In 1998, Celanese AG would have had pro forma sales of around EUR 5.2 billion. Celanese AG will be demerged with retroactive effect from January 2, 1999 and will have net debt totaling EUR 1 billion.

As announced in 1998, in October Hoechst AG shareholders are to receive one share in Celanese AG for every 10 Hoechst shares they own. The shares in Celanese AG are expected to be listed on the New York and Frankfurt Stock Exchanges in October 1999.

Claudio Sonder will serve as the future Chairman of the Board of Management of Celanese AG. The Celanese Board of Management will also comprise Ernst Schadow (Director of Personnel, responsible for Affiliates, Environmental Protection and Technology), Perry W. Premdas (Chief Financial Officer), Knut Zeptner (Celanese Chemicals and Acetate, Edward H. Munõz (Ticona
Technical Polymers). Günter Metz is to be elected Chairman of the Supervisory Board.

The Aventis project is subject to the approval of the shareholders of Hoechst and Rhône-Poulenc. The Celanese project is also subject to the approval of the Hoechst shareholders. Both projects are subject to the proceedings of information and consultation of the employee representatives,
and clearance by the antitrust, fiscal and other relevant authorities.

Statements in this news release other than historical information are forward-looking statements subject to risks and uncertainties. Actual results could differ materially depending on factors such as the availability of resources, the timing and effects of regulatory actions, the strength of competition, the outcome of litigation, and the effectiveness of patent protection. Additional information regarding risks and uncertainties is set forth in the 1998 Hoechst AG Annual Report on Form 20-F and other documents of Hoechst AG on file with the Securities and Exchange
Commission.

Company news release
N1803