To assess the differential effects of the perceived benefits and costs associated with both condom use and unprotected sex on sexual risk behaviors, data were collected from 704 ethnically diverse male and female sexually experienced late adolescent college students (aged 17-25). Perceived benefits and costs for condom use and perceived benefits and costs for unprotected sex were measured separately through an anonymous self-report survey. In addition, participants completed measures of self-efficacy for practicing safer sex and temptation for unsafe sex in various situations, and three measures of sexual risk-taking (stage of change for condom use, consistency of condom use during the past month, and whether or not a condom was used for the last act of intercourse). Univariate analyses indicated that benefits and costs of condom use, benefits of unprotected sex, self-efficacy and situational temptation were all related to sexual risk-taking. Gender differences were identified, with females reporting more benefits of condom use and costs of unprotected sex, fewer benefits of unprotected sex and costs of condom use, greater self-efficacy for practicing safer sex, and less situational temptation for unsafe sex. Multivariate analyses indicated that sexual risk behaviors were most related to situational temptation, self-efficacy for safer sex, and perceived benefits of unprotected sex. The results suggest that, among late adolescents, perceived benefits of the unhealthy behavior (unprotected sex) were better determinants of sexual risk-taking than were perceived benefits (or costs) associated with the healthy behavior (condom use). Perceived costs associated with unprotected sex were unrelated to sexual behaviors. These findings support previous work identifying adolescents as more driven by their perceptions of the positive benefits associated with risky behaviors, rather than knowledge of the costs or dangers involved in risk-taking.