A division of labor is mediated by exchange of valued goods and services. We use social exchange theory to extend this principal to "labors of love." Sexual activity in a close personal relationship seems outside the domain of bargaining and exchange. Nevertheless, we explore the possibility that this most intimate of human relations is influenced by exchange mechanisms. We derive exchange-theoretic predictions about the level of sexual effort and test these using U.S. survey data on sexual behavior. Results provide modest support for the predictions. Sexual favors are reciprocated, and individuals offer greater sexual gratification to partners who are themselves more sexually generous and less emotionally attached. Evidence is inconclusive for the effects of relative income, physical attractiveness and household chores.