The loss of sexual receptivity displayed by once-mated female house flies, Musca domestica L., was investigated by repeatedly mating males to deplete the accessory secretion responsible for inducing this behavior. With each successive mating, there was a step-wise increase in the amount of time spent in copulo and in the number of females remating that were first crossed with previously mated males. Mating pairs containing males that had copulated three times before remained in copulo about twice as long as pairs containing virgin males. The remating of females initially crossed with virgin males was 3% as compared to 21% for those females crossed with males that had mated three times previously. These phenomena are apparently related to the titer of male accessory secretion reaching the receptor site(s) in the female that induce mating refusal behavior. The brain of the female apears to have some control over the loss of mating receptivity since mating inhibition was not displayed by females that had been decapitated or had their brains destroyed.