This article contains empirical tests of the information-motivation-behavioral skills (IMB) model of AIDS-preventive behavior (J.D. Fisher & Fisher, 1992; W.A. Fisher & Fisher, 1993a), which has been designed to understand and predict the practice of AIDS-preventive acts. The IMB model holds that AIDS-preventive behavior is a function of individuals' information about AIDS prevention, motivation to engage in AIDS prevention, and behavioral skills for performing the specific acts involved in prevention. The model further assumes that AIDS-prevention information and motivation generally work through AIDS-prevention behavioral skills to influence the initiation and maintenance of AIDS-preventive behavior. Supportive tests of the model, using structural equation modeling techniques, are reported with populations of gay male affinity group members (n = 91) and heterosexual university students (n = 174).