Abstract: Method for authenticating a user for the purposes of establishing a connection from a mobile terminal to a WLAN network A user in a telecommunications network wishes do use a WLAN access. To do this he needs a WLAN authentication token, a login and a password. The key point of the invention is that, for the transmission and communication of the authentication data to the WLAN, it is not the SMS protocol which is used but the alternative USSD (Unstructured Supplementary Service Data) protocol. These so-called USSD strings can be easily entered by users on their terminal keypads. The USSD string is then not sent to the SMS gateway, as in the known method, but is sent directly to the Home Location Register (HLR) of the mobile radio network.