Summary This paper describes the mobility management mechanisms for mobile telecommunications networks. There are two major types of mobility: radio network mobility and core network mobility. Radio network mobility supports radio link switching of a mobile user during conversation, and core network mobility provides roaming and tunnelrelated management for packet re-routing due to user movement. Impact of mobility on both the radio and the core networks is addressed in this paper. Also, potential research issues on these topics are discussed. Copyright # 2005 John Wiley & Sons, Ltd.