Abstract: In a mobile communication system in which the service area is covered with a plurality of location registration areas each having a plurality of cells each relating to a specific base station, each location registration area has a plurality of groups so that the cells belonging to any group overlaps partly with the cells of other groups, but do not completely coincide with cells of other groups, and each mobile station belongs to one of said groups. When a mobile station moves beyond the border of location registration areas, the location updating for the mobile station is carried out at the cell in which the mobile station stays. In that case, as the mobile stations are classified into a plurality of groups, the traffic in each cell for location updating is dispersed to many cells, and the maximum traffic density for location updating per cell is reduced. So, the number of control channels in the system for location updating may be reduced.