This study investigates the sexual self-efficacy and sexual self-esteem of males and females and the relation between sexual risk-taking and these self-perceptions. Sexually active 18-yearolds were administered measures of sexual self-efficacy and sexual self-esteem and were asked about their sexual behaviour. Males had higher levels of self-esteem and were more confident than females of their ability to assert their sexual needs, but less confident that they could say no to sexual demands. For a substantial minority there were some difficulties in dealing with condoms. Competence in the sexual domain accounted for a significant but small amount of variance in sexual risk-taking. The predictors of sexual risk-taking were the same for both sexes but differed according to type of partner. Confidence in the ability to say no was the sole predictor of safer sexual behaviour with a casual sex partner. In addition to this factor, lower levels of risk with a regular partner were predicted by these respondents' lower confidence in the ability to assert their sexual needs, together with lower levels of their own sexual self-worth. There is need for adolescents to achieve a sense of mastery and self-worth in the sexual domain, as well as an understanding of the nature of 'regular' relationships.