Two populations of eastern chipmunks (Tamias striatus) were studied with respect to botfly parasitism (Cuterebra emasculator) in northern Michigan during the summers of 1982 and 1983. Parasitism was correlated with a significant decrease in above ground activity, however all individuals displayed some depression of activity during late summer (summer lull). Weight, home range dynamics, reproduction, and overwintering abilities ere unaffected by botflies. Males displayed significantly larger home ranges and acquired significantly more botflies than females.