Selection for a decrease in time from 1st to 2nd mating was carried out on a strain of D. melanogaster for over 20 generations. Selection was successful in reducing the average time to remating by .apprx. 3 days. The behavior of both sexes was affected by the selection process. The mode of inheritance was not typically polygenic. Reciprocal hybridizations of the selected strain with the control strain indicated X chromosome involvement and recessive gene action. Correlated responses to selection were also investigated. Speed to 1st mating and locomotor activity were unchanged by selection, but male courtship persistence was increased and female productivity decreased in the selected strain. The techniques used to study repeated mating in the laboratory are discussed.