Research on error management theory indicates that men tend to overestimate women's sexual interest and women underestimate men's interest in committed relationships (Haselton & Buss, 2000). We test the assumptions of the theory in face-to-face, stranger interactions with 111 man-woman dyads. Support for the theory emerges, but potential boundary conditions are observed. In addition, we find that women's perceptions of men's desire for commitment is related to the women's own self-reported sexual interest but that the reverse does not hold for men. Finally, we find evidence consistent with the proposition that people project their own level of interest in sex or in a committed relationship onto their interaction partners.