Changes in home range size in 7 groups of rhesus monkeys were observed in urban and forest habitats in north India. In three groups home range size decreased due to either emigration or trapping of the alpha male. The average reduction in home range size was 30.48%. In one group the home range decreased from 1·12 km2 to 0·46 km2 after the removal of all group members except alpha male. The home ranges of 3 groups increased slightly due to disturbance caused (a) by elephants, (b) by trapping and (c) by conspecific group. The increase in the home range was for a short period (less than 15 days) as long as the disturbing variable was present. However, the decrease in home range due to loss of alpha male was almost permanent. The importance of the personality of alpha male and his personal experiences in the maintenance of home range has been discussed.