Psychological determinants of AIDS-preventive behaviors were examined from the perspective of the theory of reasoned action in prospective studies of gay men, heterosexual university students, and heterosexual high school students. Across samples, preventive behaviors, and prospective intervals of 1 and 2 months' duration. AIDS-preventive behaviors were predicted by behavioral intentions; behavioral intentions were a function of attitudes and norms; and attitudes and norms were a function of their theorized basic underpinnings. Discussion focuses on the development of AIDS-prevention interventions that modify intentions, attitudes, and norms concerning performance of AIDS-preventive behaviors by targeting the empirically identified underpinnings of attitudes and norms related to specific preventive behaviors in specific populations of interest.