This study was conducted to assess the level of AIDS-related knowledge, attitudes, and risk behaviors of a group of predominantly sexually active high school seniors (N=734) and to evaluate the relative effectiveness of three AIDS prevention activities in improving knowledge, attitudes, and behaviors among these students. The educational program consisted of two parts. First, a slide show/lecture was given by an AIDS specialist, which focused on basic facts about AIDS and presented the personal stories of several young patients. Second, students participated in small group sessions in one of three AIDS prevention activities: a question and answer session, a presentation by a young person with AIDS (PWA), and a role playing activity. Sessions leaders and health and physical education teachers from participating schools were trained by the research team. Data were gathered by testing AIDS-related knowledge and attitudes prior to and following the slide show/lecture and a questionnaire after participation in small group activities. Five weeks later, students completed a knowledge and attitudes delayed posttest as well as a questionnaire on which behavioral changes related to AIDS were reported. Results indicate that significant gains were made in attitudes towards PWAs and in decreasing risk behaviors. (LL)