A bstract An event-speci® c analysis was conducted in order to assess the relative importance of a number of predictors of condom use. Surveys were completed by 271 heterosexual tertiary students: 60% used a condom in their most recent sexual encounter. Condo m use was more closely related to state-like characteristics of the sexual encounter (e.g. having an agreement to use a condo m, use of other form s of contraception) than trait-like characteristics of the individual (e.g. attitudes toward condom use, perceived risk of infection w ith HIV or other STD s). In addition, condom use was more strongly in¯uenced by concerns about pregnancy prevention than concerns about disease prevention. The results of this study show that if we are to understand why heterosexual young adults do not consistently use condoms then we cannot only examine trait-like characteristics of the individual. W e m ust also exam ine the context of speci® c sexual encounters.