Meat-eating and hunting behavior by blue monkeys (Cercopithecus mitis) was observed on several occasions in the Kalinzu Forest, Uganda. The monkeys ate three squirrels and a frog. Multiple members of a group comprising more than 10 individuals engaged in repeated simultaneous hunts on the ground for about 2 weeks following the first meat-eating episode. Blue monkeys in the Kalinzu Forest do not often eat meat; however, such behavior may occur intensively for short periods. It is possible that the initial predation provoked subsequent hunting attempts in the rest of the group. This "hunting craze" ceased after 2 weeks. The predatory tendency appeared to be motivated by some social factor, such as other members' success, because there was no evidence for the influence of an environmental factor.