Ascertaining the authentication of a roaming subscriber

A method for a first home service provider to ascertain that a mobile station of one of its subscriber, when roaming into a service area of a second service provider, has been authenticated by the second service provider is provided. The method includes the second service provider sending location information of the subscriber to the first service provider via e.g. a location update request, and the mobile station sending information to the first service provider indicating that the mobile station has been authenticated by the second service provider e.g. authentication status. A mobile station and a server for implementing the method are also disclosed.