A mobile communication system in which overlapping location areas are defined by radio base stations on an autonomous distribution basis. In a first embodiment, a mobile station registers the location thereof when moved in a radio zone which is not included in a location area notified by a radio base station and held therein. In a second embodiment, the mobile station registers the location when entered a radio zone in which location area being notified by the radio base station does not include the radio zone where the mobile station registered the location last. In a first and a second embodiment, the mobile station memorizes radio zones which it has passed after location registration as route information and may report the route information to a radio base station in the event of next location registration. The radio base station sequentially includes in the location area the radio zones which frequently appear in the route information. In a third embodiment, in response to a terminating call meant for the mobile station, a mobile switching center sends a calling signal meant for the mobile station to all of the radio base stations. In response, each radio base station effects calling if the own location area where it is situated is coincident with a location area included in the calling signal. In a fourth to a sixth embodiment, each radio base station measures the traffic of registration signals or that of calling signals so as to increase or decrease the number of radio zones included in the own location area in matching relation to the measured traffic.