A method for optimizing the load distribution between one mobile radio network, for example using the UMTS standard, and another mobile radio network, for example using the GSM standard, by optimizing the signalling sequence when establishing a connection in such a mobile radio system. It enables efficient cooperation when establishing a connection, for example a voice connection, between a UMTS and a GSM network. In addition to the efficient use of resources in a UMTS system, the method also enables direct establishment of a connection, for example of a voice connection that was initiated in a UMTS network, in a GSM network.