Leadership changes accompanied by infanticide are described for two langur troops at Abu, Rajasthan. These events are compared with similar reports from Dharwar and Jodhpur. In each of seven cases, infanticide occurred when males entered the troop from outside it. Females whose infants were killed subsequently exhibited estrous behavior and copulated with the new leader. In three troops at Dharwar and Abu, seventy percent of females who lost infants gave birth within eight months. In these cases, infanticide appears on average to increase the reproductive success of the incoming male. Confronted with a male reproductive strategy disadvantageous for them, females respond to usurping males with various counter-strategies. From a comparison with other mammals, infant-killing by males may be advantageous (1) when there is intense competition for females; and (2) when frequent take-overs potentially curtail the tenure of an incoming leader.