Abstract: A method for establishing a multimedia session between a calling telecommunications equipment and a called equipment that is a mobile equipment of a network of the multimedia sub-domain type, wherein: an invitation (Invite) is sent from the first user equipment (UE1) to establish a multimedia session, which comprises as he destination address a public identity of the second equipment, said invitation being transmitted: by the first equipment (UE1) to a first proxy server (P-CSCF1), then, from this first proxy server, to a first session control server (S-CSCF1) of the network in which the first equipment (UE1) is registered, and from this first session server (S-CSCF1) to a point of entry server (I-CSCF2) of the network corresponding to the destination address of the second equipment (UE2); this point of entry server (I-CSCF2) interrogates a database (HSS2) of the network of the second equipment (UE2) in order to obtain the address of a session control server (S-CSF2) responsible for said second equipme