The support of multicasting as a network layer service poses stringent requirements to next generation mobile networks. But for the fact that IP multicasting has been considered in wireless networks, not until recently has there been a first attempt for the multimedia broadcast/multicast service (MBMS) support in UMTS. The investigation of MBMS architectural and functional design in respect to session and mobility management is the major focus of this paper. We approach mobility management support for idle- and connectedmode users with activated MBMS sessions as an extension to the existing mechanisms applicable to point-to-point communication. Moreover, we move one step further to the integration of the UMTS with the IP world, by replacing the UMTS core network with a fully IP-enabled network and propose mobility management mechanisms, in this integrated environment, for users receiving MBMS data.