Amendment No. 3

Sanofi-Synthélabo

N/A

John Spinnato

Copies to:

      Approximate date of commencement of proposed sale of the securities to the public: As soon as practicable after this Registration Statement becomes effective and all other conditions to the consummation of the transaction described herein have been satisfied or waived.

      If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. o

      If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. o

      The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until this Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

The information contained herein is subject to completion or amendment. A registration statement relating to these securities has been filed with the United States Securities and Exchange Commission. These securities may not be sold nor may offers to buy be accepted prior to the time the registration statement becomes effective. This prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities, nor shall there be any sale of these securities, in any jurisdiction in which such offer, solicitation or sale is not permitted or would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction.

SUBJECT TO COMPLETION. DATED APRIL 7, 2004.

Offer to Exchange

In this exchange offer, we are offering:

	•	0.8333 of a newly issued ordinary share, nominal value €2 per share, of Sanofi-Synthelabo and €11.50 in cash, without interest, in exchange for each ordinary share of Aventis tendered; and
	•	1.6667 newly issued American depositary shares, or ADSs (each ADS representing one-half of one Sanofi-Synthelabo ordinary share), of Sanofi-Synthelabo and an amount in U.S. dollars equal to €11.50, in cash, without interest, in exchange for each Aventis ADS (each Aventis ADS representing one Aventis ordinary share) tendered.

This exchange offer includes a mix and match election feature that allows holders of Aventis ordinary shares, including Aventis ordinary shares represented by Aventis ADSs, to elect to receive, in lieu of the mix of consideration described above:

	•	1.0294 newly issued Sanofi-Synthelabo ordinary shares in exchange for each Aventis ordinary share tendered; or 2.0588 newly issued Sanofi-Synthelabo ADSs in exchange for each Aventis ADS tendered; or
	•	€60.43 in cash, without interest, in exchange for each ordinary share of Aventis tendered; or an amount in U.S. dollars equal to €60.43, in cash, without interest, in exchange for each Aventis ADS tendered.

The mix and match elections are subject to proration and allocation adjustments that will ensure that, in the aggregate (and subject to adjustment if Aventis pays any dividend or interim dividend before the settlement of the offers), 81.0% of the Aventis ordinary shares (including Aventis ordinary shares underlying the Aventis ADSs) tendered in the U.S. offer and the concurrent French offer and German offer will be exchanged for Sanofi-Synthelabo ordinary shares (including Sanofi-Synthelabo ordinary shares underlying Sanofi-Synthelabo ADSs) and 19.0% will be purchased for cash. See “The U.S. Offer — Mix and Match Election”.

If Aventis pays any dividend or any interim dividend in respect of the Aventis ordinary shares, including Aventis ordinary shares represented by Aventis ADSs, before the settlement of the offers, the consideration offered in exchange for each Aventis ordinary share and each Aventis ADS tendered will be reduced by an amount equal to the net value of the dividend paid per Aventis ordinary share in the manner described under “The U.S. Offer — Consideration Offered after Payment of Aventis Dividends”. In respect of any Sanofi-Synthelabo ordinary share, including any Sanofi-Synthelabo ordinary shares represented by Sanofi-Synthelabo ADSs, that you receive in exchange for the Aventis ordinary shares or the Aventis ADSs that you tender in this exchange offer, you will be entitled to receive any annual dividend with respect to Sanofi-Synthelabo’s 2003 results that is declared on the Sanofi-Synthelabo ordinary shares and any other dividend that is paid after the settlement of this exchange offer. See “The U.S. Offer — Entitlement to Sanofi-Synthelabo Dividends”.

The U.S. offer will expire at 5:00 p.m., New York City time, on May 28, 2004, unless it is extended or is withdrawn prior to that time. You may withdraw any Aventis securities tendered at any time prior to the expiration time.

Sanofi-Synthelabo is offering to acquire all of the outstanding Aventis ordinary shares through three separate offers. See “The U.S. Offer — The U.S. Offer, the French Offer and the German Offer”. Together, these offers are being made for all issued and outstanding Aventis ordinary shares, including Aventis ordinary shares represented by Aventis ADSs, and all Aventis ordinary shares that are or may become issuable prior to the expiration of the offers due to the exercise of outstanding Aventis subscription stock options or the exercise of outstanding Aventis warrants (Bons de souscription d’actions, or BSAs). Sanofi-Synthelabo will issue up to approximately 158,333,333 Sanofi-Synthelabo ordinary shares (including Sanofi-Synthelabo ordinary shares represented by Sanofi-Synthelabo ADSs) pursuant to this U.S. offer. The completion of the offers is subject to a minimum tender condition, among others. For a discussion of these conditions, see “The U.S. Offer — Conditions to the U.S. Offer”. Subject to applicable law and regulations, we reserve the right to modify or waive this condition in our discretion.

For a discussion of the risk factors that you should consider carefully in evaluating the U.S. offer, see “Risk Factors” beginning on page 22.

Sanofi-Synthelabo ordinary shares are listed on Euronext Paris and the New York Stock Exchange, or NYSE, and trade on the Premier Marché of Euronext Paris under the symbol “SAN”. Sanofi-Synthelabo ADSs are listed on the NYSE and trade under the symbol “SNY”.

Neither the United States Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities to be issued in connection with this offer or has passed upon the adequacy or accuracy of the disclosure in this document. Any representation to the contrary is a criminal offense in the United States.

The date of this prospectus is April [l], 2004.

CERTAIN DEFINED TERMS

Unless otherwise specified or if the context so requires:

	•	References in this prospectus to “Sanofi-Synthelabo,” the “company,” “we,” “us” or “our” refer to Sanofi-Synthelabo, a French société anonyme, and, where applicable, its consolidated subsidiaries.
	•	References to “Aventis” refer to Aventis, a French société anonyme, and, where applicable, its consolidated subsidiaries.
	•	References to “Aventis securities” refer collectively to the Aventis ordinary shares and the Aventis ADSs.
	•	References to “Sanofi-Synthelabo securities” refer collectively to the Sanofi-Synthelabo ordinary shares and the Sanofi-Synthelabo ADSs.
	•	References to “Aventis BSAs” refer to the series of Aventis warrants (Bons de souscription d’actions) that were issued to two employee funds, the units of which were subscribed by German employees.
	•	References to the “related U.S. offer documents” refer collectively to the form of acceptance, the ADS letter of transmittal and the notice of guaranteed delivery included with this document.
	•	References to “Merrill Lynch (France)” refer to Merrill Lynch Capital Markets (France) S.A.S., an affiliate of Merrill Lynch & Co.

INFORMATION INCORPORATED BY REFERENCE

This prospectus incorporates important business and financial information about Sanofi-Synthelabo and Aventis by reference and, as a result, this information is not included in or delivered with this prospectus. For a list of those documents that are incorporated by reference into this prospectus, see “Additional Information for Securityholders — Incorporation of Certain Documents by Reference” on page 150.

Documents incorporated by reference are available from us upon oral or written request without charge. You may also obtain documents incorporated by reference into this prospectus from the Internet site of the United States Securities and Exchange Commission, or SEC, at the URL (or uniform resource locator) http://www.sec.gov or by requesting them in writing or by telephone from the information agent for these offers:

MacKenzie Partners, Inc.

To obtain timely delivery of these documents, you must request them by no later than May 21, 2004.

In deciding whether to tender your Aventis securities in the exchange offer described in this prospectus, you should rely only on the information contained or incorporated by reference into this prospectus or in the related U.S. offer documents. Sanofi-Synthelabo has not authorized any person to provide you with any information that is different from, or in addition to, the information that is contained in this prospectus or in the related offer documents.

The information contained in this prospectus speaks only as of the date indicated on the cover of this prospectus unless the information specifically indicates that another date applies.

REGULATORY STATEMENT

The exchange offer described in this prospectus is subject to the applicable laws and regulations of France, including the rules and regulations of the Autorité des marchés financiers, or AMF, of Germany, including the German Securities Sales Prospectus Act (Wertpapier-Verkaufsprospektgesetz), and of the United States, including the tender offer rules applicable to equity securities registered under Section 12 of the United States Securities Exchange Act of 1934, as amended, or the Exchange Act. This U.S. offer document constitutes a prospectus under Section 5 of the United States Securities Act of 1933, as amended, or the Securities Act, with respect to the Sanofi-Synthelabo ordinary shares to be issued on completion of the U.S. offer. References in this prospectus to the rules and regulations of, and filings made with, the AMF, include the rules and regulations of, and filings made with, the former Conseil des marchés financiers, or CMF, and the former Commission des opérations de bourse, or COB, as applicable. The CMF and the COB were merged to form the AMF, effective as of November 24, 2003.

This prospectus is not an offer to sell securities and it is not soliciting an offer to buy securities, nor shall there be any sale or purchase of securities pursuant hereto, in any jurisdiction in which such offer, solicitation or sale is not permitted or would be unlawful prior to registration or qualification under the laws of any such jurisdiction.

This prospectus has not received the visa of the French Autorité des marchés financiers, or AMF, or the German Bundesanstalt für Finanzdienstleistungsaufsicht, or BAFin. Accordingly, this prospectus may not be used to make offers or sales in France or Germany in connection with any offer described herein.

TABLE OF CONTENTS

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PRESENTATION OF CERTAIN FINANCIAL AND OTHER INFORMATION

      Sanofi-Synthelabo has included in this prospectus information concerning Aventis known to Sanofi-Synthelabo based on publicly available information (primarily filings by Aventis with the SEC and the AMF). Non-public information concerning Aventis was not available to Sanofi-Synthelabo for the purpose of preparing this prospectus. Publicly available information concerning Aventis may contain errors. Sanofi-Synthelabo has no knowledge that would indicate that any statement relating to Aventis contained or incorporated by reference into this prospectus is inaccurate or incomplete. However, Sanofi-Synthelabo was not involved in the preparation of those statements and cannot verify them. Pursuant to Rule 409 under the Securities Act and Rule 12b-21 under the Exchange Act, Sanofi-Synthelabo has requested that Aventis provide Sanofi-Synthelabo with information required for complete disclosure regarding the businesses, operations, financial condition and management of Aventis. Sanofi-Synthelabo will amend or supplement this prospectus to provide any information that Sanofi-Synthelabo receives from Aventis, if Sanofi-Synthelabo receives the information before the U.S. offer expires and Sanofi-Synthelabo considers it to be material, reliable and appropriate. As of the date of this prospectus, no such information has been received from Aventis.

ACCOUNTING PRINCIPLES

Sanofi-Synthelabo

      Sanofi-Synthelabo prepares its consolidated financial statements in accordance with French generally accepted accounting principles (commonly known as French GAAP), which differ in certain significant respects from United States generally accepted accounting principles (commonly known as U.S. GAAP). For a detailed discussion of the differences between French GAAP and U.S. GAAP as they relate to Sanofi-Synthelabo’s consolidated financial statements, and for a reconciliation of net income and shareholders’ equity and condensed consolidated U.S. GAAP statements of income and balance sheets, as of the dates and for the periods indicated, please see Note G to Sanofi-Synthelabo’s audited consolidated financial statements included in its Annual Report on Form 20-F for the year ended December 31, 2003, which is incorporated by reference into this prospectus. See “Additional Information for Securityholders — Incorporation of Certain Documents by Reference” on page 150.

Aventis

      Aventis prepares its consolidated financial statements in accordance with French GAAP. For a detailed discussion of the differences between French GAAP and U.S. GAAP as they relate to Aventis’s consolidated financial statements, and for a reconciliation of net income and shareholders’ equity and condensed consolidated U.S. GAAP statements of income, balance sheets and cash flow statements, as of the dates and for the periods indicated, please see Note 34 to Aventis’s audited consolidated financial statements included in its Annual Report on Form 20-F for the year ended December 31, 2003, which is incorporated by reference into this prospectus. See “Additional Information for Securityholders — Incorporation of Certain Documents by Reference” on page 150.

CURRENCIES

In this prospectus, unless otherwise specified or the context otherwise requires:

	•	“$,” “U.S. $” or “U.S. dollar” each refers to the United States dollar; and
	•	“€” or “euro” each refers to the euro, the single currency established for members of the European Economic and Monetary Union, or the EMU, since January 1, 1999.

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Each of Sanofi-Synthelabo and Aventis publishes its consolidated financial statements in euros. This prospectus contains translations of some euro amounts into U.S. dollars. These amounts are provided solely for your convenience. On April 6, 2004, the most recent practicable date prior to the date of this document, the Federal Reserve Bank of New York noon buying rate was €1.00 = $1.2089. See “Exchange Rate Information” for additional information regarding the exchange rates between the euro and the U.S. dollar.

NO INTERNET SITE IS PART OF THIS PROSPECTUS

Each of Sanofi-Synthelabo and Aventis maintains an Internet site. The Sanofi-Synthelabo Internet site is at the URL http://www.sanofi-synthelabo.com. The Aventis Internet site is at the URL http://www.aventis.com. Information contained in or otherwise accessible through these Internet sites is not a part of this prospectus. All references in this prospectus to these Internet sites are inactive textual references to these URLs and are for your information only.

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QUESTIONS AND ANSWERS ABOUT THE U.S. OFFER

A:	We are making the U.S. offer and the concurrent French and German offers to acquire control of Aventis through the acquisition of all or a substantial portion of the outstanding Aventis ordinary shares, including Aventis ordinary shares represented by Aventis ADSs.
	Sanofi-Synthelabo is seeking to acquire Aventis because Sanofi-Synthelabo believes that the combination of the two companies will create the number one pharmaceutical company in Europe and the number three worldwide. Sanofi-Synthelabo believes that the enhanced scale, financial strength and research and development resources of the combined company should allow it to serve patients worldwide and to enhance shareholder value in ways that are not likely to be achieved by either Sanofi-Synthelabo or Aventis on a stand-alone basis. Sanofi-Synthelabo believes that the strategic rationale for the acquisition is compelling; however, as with any investment decision there can be no assurance that the anticipated benefits will be realized. For a discussion of the risk factors that you should consider carefully in evaluating the U.S. offer, see “Risk Factors”.

A:	We are making three offers for legal reasons in order to satisfy regulatory requirements.

A:	The French offer, the German offer and the U.S. offer are being made on substantially similar terms and completion of the offers is subject to the same conditions.
	The U.S. offer is open to all holders of Aventis ordinary shares who are located in the United States and to all holders of Aventis ADSs, wherever located.
	The French offer is open to all holders of Aventis ordinary shares who are located in France and to holders of Aventis ordinary shares who are located outside of France, Germany and the United States, if, pursuant to the local laws and regulations applicable to such holders, they are permitted to participate in the French offer.
	The German offer is open to all holders of Aventis ordinary shares who are located in Germany.

A:	No. Holders of Aventis ordinary shares who are located in the United States and all holders of Aventis ADSs, wherever located, do not have the right to tender their Aventis securities in the French offer or the German offer. You must follow the procedures set forth in this prospectus to tender your Aventis ordinary shares or Aventis ADSs in the U.S. offer.

A:	For each Aventis ordinary share validly tendered and not withdrawn, unless you make a mix and match election, you will receive:

	•	€11.50 in cash, and
	•	0.8333 of a Sanofi-Synthelabo ordinary share.

	For each Aventis ADS (each representing one Aventis ordinary share) validly tendered and not withdrawn, unless you make a mix and match election, you will receive:

	•	an amount in U.S. dollars equal to €11.50 in cash, and
	•	1.6667 Sanofi-Synthelabo ADSs (each representing one-half of one Sanofi-Synthelabo ordinary share).

	In no event will you receive any interest on the payments to which you are entitled under the U.S. offer.
	The cash consideration paid to tendering holders of Aventis ordinary shares will be paid in euros. The cash consideration paid to tendering holders of Aventis ADSs will be converted into U.S. dollars on the day that it is received by the U.S. ADS exchange agent at the then prevailing spot market rate and distributed, net of any

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	expenses incurred, to the tendering holders of Aventis ADSs.
	Based on a price of €58.72 per Sanofi-Synthelabo ordinary share, which was the average daily closing price, weighted by volume, for Sanofi-Synthelabo ordinary shares on Euronext Paris during the calendar month ended on January 21, 2004, the terms of the U.S. offer value each Aventis ordinary share at €60.43, representing a premium of 15.2% over the average daily closing price, weighted by volume, for Aventis ordinary shares on Euronext Paris during the same period, which was €52.46 per Aventis ordinary share. Based on the closing price of €57.75 for Sanofi-Synthelabo ordinary shares on Euronext Paris on January 23, 2004, the last trading day before the public announcement of the U.S. offer, the terms of the U.S. offer value each Aventis ordinary share at €59.63, representing a premium of 3.6% over the closing price of €57.55 for Aventis ordinary shares on Euronext Paris on that date. Based on the closing price of €53.50 for Sanofi-Synthelabo ordinary shares on Euronext Paris on April 6, 2004, the most recent practicable trading day prior to the date of this prospectus, the terms of the U.S. offer value each Aventis ordinary share at €56.08, representing a discount of (10.4)% to the closing price of €62.60 for Aventis ordinary shares on Euronext Paris on that date.
	Based on a price of $37.05 per Sanofi-Synthelabo ADS, which was the average daily closing price, weighted by volume, for Sanofi-Synthelabo ADSs on the NYSE during the calendar month ended on January 21, 2004, and the average exchange rate of €1 = $1.2606 during the same period, the terms of the U.S. offer value each Aventis ADS at $76.24, representing a premium of 14.7% over the average daily closing price, weighted by volume, for Aventis ADSs on the NYSE during the same period, which was $66.50 per Aventis ADS. Based on the closing price of $37.01 for Sanofi-Synthelabo ADSs on the NYSE on January 23, 2004, the last trading day before the public announcement of the U.S. offer, and an exchange rate of €1 = $1.2610, the terms of the U.S. offer value each Aventis ADS at $76.18, representing a premium of 4.4% over the closing price of $73.00 for Aventis ADSs on the NYSE on that date. Based on the closing price of $32.60 for Sanofi-Synthelabo ADSs on the NYSE on April 6, 2004, the most recent practicable trading day prior to the date of this prospectus, and an exchange rate of €1 = $1.2089, the terms of the U.S. offer value each Aventis ADS at $68.24, representing a discount of (10.0)% to the closing price of $75.85 for Aventis ADSs on the NYSE on that date.

A:	Yes. The U.S. offer includes a mix and match election feature whereby you may elect to receive only Sanofi-Synthelabo ordinary shares or Sanofi-Synthelabo ADSs, as applicable, or only cash in exchange for any or all of the Aventis securities that you tender. However, these elections will be satisfied in full only to the extent that off-setting elections have been made by other tendering holders of Aventis securities in the U.S. offer, the French offer and the German offer.  Accordingly, there can be no assurance that you will receive all of your consideration in the form that you have elected.
	You are not required to make any election (in which case you will automatically receive the standard entitlement) or to make the same election for all the Aventis securities that you tender.
	The election procedure is described more fully in the section captioned, “The U.S. Offer — Mix and Match Election”. Any holder of Aventis securities who wishes to make a mix and match election should carefully read and comply with the instructions in the accompanying form of acceptance or the ADS letter of transmittal, as applicable.
	See “Risk Factors — If you make an all stock or all cash election there can be no assurance that you will receive all your consideration in the form you elected or that your election will result in the same mix of consideration regardless whether you tender your Aventis securities in the initial offer period or in the subsequent offering period, if any; in any event, you will not know the exact mix of consideration that you will receive until after

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	the applicable expiration date and you are no longer able to withdraw your tender.”

A:

Yes. If Aventis pays any dividend or any interim dividend in respect of the Aventis ordinary shares, including Aventis ordinary shares represented by Aventis ADSs, before the settlement of the U.S. offer, the consideration offered in exchange for each Aventis ordinary share and each Aventis ADS tendered will be reduced by an amount equal to the net value of the dividend paid per Aventis ordinary share, in the manner described under “The U.S. Offer — Consideration Offered after Payment of Aventis Dividends”.

A:	Yes. In respect of the Sanofi-Synthelabo ordinary shares, including Sanofi-Synthelabo ordinary shares represented by Sanofi-Synthelabo ADSs, you will be entitled to receive:

	•	any annual dividend that is approved to be paid with respect to Sanofi-Synthelabo’s 2003 results, and
	•	any other dividend that is paid after the settlement of the offers.

	See “The U.S. Offer — Entitlement to Sanofi-Synthelabo Dividends”.

A:	If all of the Aventis securities are validly tendered and exchanged, pursuant to the terms of the U.S. offer, the French offer and the German offer, immediately after the exchange, on a diluted basis taking into account all in-the-money options and BSAs that are exercisable as of the expected closing date:

	•	the former holders, other than Aventis, of Aventis securities will own approximately 49% of the share capital and approximately 39% of the voting rights of Sanofi-Synthelabo, and
	•	the current holders, other than Sanofi-Synthelabo, of Sanofi-Synthelabo securities will hold approximately 51% of the share capital and approximately 61% of the voting rights of Sanofi-Synthelabo.

	After completion of the offers, you will hold securities of a company larger than Aventis. Accordingly, you will have lower ownership and voting percentages of Sanofi-Synthelabo than you now have in Aventis.

A:	We will only extend the expiration date of the U.S. offer in order to coordinate the expiration dates of the U.S. offer and the French offer. Only the Autorité des marchés financiers, or AMF, has the authority to set or to extend the expiration date of the French offer. Accordingly, we will extend the expiration date of the U.S. offer only if:

	•	the AMF sets a date later than May 28, 2004 for the expiration of the French offer, or
	•	the AMF has not set an expiration date for the French offer by May 28, 2004, or
	•	the AMF subsequently extends the French offer.

A:	If we extend the U.S. offer we will issue a press release. Our press release will set forth the expiration date and time of the extended U.S. offer and inform holders of Aventis securities that they may tender, or withdraw their

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	tendered, Aventis securities at any time until the expiration of the offer period, as extended.

A:	Yes. Sanofi-Synthelabo is not obligated to purchase any tendered Aventis securities unless Aventis securities representing at least 50% of the total share capital and voting rights in Aventis, calculated on a fully diluted basis, plus one Aventis ordinary share are tendered in the U.S. offer, the French offer and the German offer, on a combined basis. We refer to this condition as the “minimum tender condition”.
	We may waive the minimum tender condition at any time on or prior to the date that is five French trading days prior to the expiration date of the offer. Our waiver of the minimum tender condition will be deemed to be an improved offer and may cause the AMF to extend the offer period; the AMF may also declare your tenders null and void. Unless we have waived the minimum condition, if the minimum tender condition is not met, the offers will not be completed.
	Sanofi-Synthelabo’s obligation to complete the offers is subject to the condition that the applicable waiting period under the U.S. Hart-Scott-Rodino Act of 1976 has expired or been terminated and no order has been entered prohibiting the transaction.
	We refer to this condition as the “antitrust condition”. Because the offers are subject to the antitrust condition, under applicable French regulations, the French offer will lapse (“est caduque”, meaning it is null and void) as soon as the U.S. Federal Trade Commission issues a second request for information before the expiration of the HSR waiting period. If the French offer lapses for this reason, we will withdraw the U.S. offer and the German offer.
	In addition, Sanofi-Synthelabo’s obligation to complete the offers is subject to the condition that the issuance of additional Sanofi-Synthelabo ordinary shares to be issued on completion of the offers has been duly approved by the shareholders of Sanofi-Synthelabo at an extraordinary meeting of shareholders to be held for this purpose. We refer to this condition as the “share issuance condition”.

A:	Yes. You may withdraw your securities at any time until the expiration date.

A:

If you hold American depositary receipts or ADRs, for Aventis ADSs, complete and sign the ADS letter of transmittal included with this document and send it, together with your ADRs and any other required documents, to the U.S. ADS exchange agent before the expiration of the U.S. offer. If your certificates are not available, you may also follow guaranteed delivery procedures described in this prospectus. Do not send your certificates to Sanofi-Synthelabo, the dealer-manager or the information agent.

A:	If you hold Aventis ADSs in book-entry form, complete the confirmation of a book-entry transfer of your Aventis ADSs into the account of the U.S. ADS exchange agent at The Depository Trust Company, commonly known as DTC, and send either an agent’s message or an ADS letter of transmittal and any other required documents to the U.S. ADS exchange agent before the expiration of the U.S. offer.

A:

If you hold Aventis ordinary shares through a U.S. custodian, you do not need to complete the ADS letter of transmittal. Instead, your U.S. custodian should either forward to you the transmittal materials and instructions sent by the French financial intermediary that holds the shares on behalf of the U.S. custodian as record owner or send you a separate form prepared by the U.S. custodian. If you have not yet received instructions from your U.S. custodian, please contact your U.S. custodian di-

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	rectly. If your Aventis ordinary shares are held in pure registered form (nominatif pur), you must first request that your shares be converted to administered registered form (nominatif administré) or to bearer form (au porteur). The conversion takes approximately one to five French business days.

A:

If you hold Aventis ordinary shares through a French financial intermediary, you do not need to complete the ADS letter of transmittal. Instead, your French financial intermediary should send you transmittal materials and instructions for accepting the U.S. offer before the last day of the offer. If you have not yet received instructions from your French financial intermediary, please contact your French financial intermediary directly. If your Aventis ordinary shares are held in pure registered form (nominatif pur), you must first request that your shares be converted to administered registered form (nominatif administré) or to bearer form (au porteur). The conversion takes approximately one to five French business days.

A:

Sanofi-Synthelabo will pay the brokerage fees, if any, and related value added taxes incurred by holders of Aventis securities tendering into the U.S. offer, up to a limit of 0.3% of the value of each Aventis security tendered, and subject to a maximum amount of €45 per account, including all taxes. Holders of Aventis securities will not be reimbursed for any brokerage fees in any event that the U.S. offer is withdrawn or is not completed because a condition has not been satisfied.

A:	If you hold exercisable Aventis stock options and you would like to tender the underlying Aventis ordinary shares into the U.S. offer, you must first exercise the options and then tender the underlying Aventis ordinary shares on or prior to the expiration date of the U.S. offer according to the instructions given in this document.
	Sanofi-Synthelabo has not had access to important information relating to Aventis’s stock option plans, including the terms of these plans. If these offers are completed, Sanofi-Synthelabo intends to offer, subject to applicable law and regulations and any applicable restrictions, to exchange Aventis stock options (including stock purchase options and stock subscription options) or the Aventis ordinary shares received as a result of exercising these stock options, as more fully described under “The U.S. Offer — Treatment of Aventis Stock Purchase Options, Aventis Stock Subscription Options and Aventis BSAs”.

A:	No. If you want to retain your Aventis securities, you do not need to take any action.

A:	If the offers for Aventis securities are withdrawn or are not successful, your Aventis securities will be returned to you without any other payment being due. This should occur within one to two French trading days following (i) the announcement of the withdrawal, or (ii) the publication by the AMF of the results of the offers, as the case may be.

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