The capital stock of Bayer AG is traded in the form of bearer shares on several German and international stock exchanges. You can buy Bayer shares through any supplier of brokerage services, usually banks. To do so, you need a custody account in which your shares are deposited. It is not possible to purchase shares directly through Bayer.
In the United States, Bayer ADRs have been traded under an OTC Level I ADR Program since September 27, 2007. The ticker symbol is BAYRY. Trading information is obtainable from the Pinksheets OTC website or financial information service providers such as Bloomberg or Reuters. Bayer ADRs are issued by The Bank of New York, acting as depositary.