We have previously reported sex differences in the effects of arginine vasopressin (AVP) on perceptual responses to same-sex faces in men and women in tests in which subjects saw emotional and neutral facial expressions. In the present study, we measured the effects of two doses of intranasal AVP, 20IU and 40IU, on responses to other-sex, as well as to same-sex neutral faces. In men, our preliminary data suggest that 20IU increases approachability ratings of female faces in subjects who are not involved in a heterosexual relationship, but decreases those ratings in men who are involved in a heterosexual relationship. In women, on the other hand, 20IU AVP appears to increase several positive responses (approachability, willingness to initiate conversation, attractiveness) towards male and female faces, but only in women who report being in a heterosexual relationship. Furthermore, those effects appear long-lasting in women, as the same effects are present 3-21 days after the initial tests. The higher dose, 40IU, did not have significant effects on behavioral responses to same- or other-sex faces in men or women. Together, these preliminary data suggest that exogenous AVP may produce dose-dependent, sex-specific influences on the processing of faces that are moderated by relationship status, and that some of its effects on the perceptions of faces may be long-lasting. We are currently increasing out sample sizes in men and women at both doses.