BACKGROUND. The number of reported cases of acquired immune deficiency syndrome (AIDS) is increasing disproportionately among Blacks in the United States. The relatively high incidence of sexually transmitted diseases among Black adolescents suggest the need for AIDS prevention programs to reduce their risk of sexually transmitted human immunodeficiency virus (HIV) infection. METHODS. Black male adolescents (n = 157) were randomly assigned to receive an AIDS risk reduction intervention aimed at increasing AIDS-related knowledge and weakening problematic attitudes toward risky sexual behavior, or to receive a control intervention on career opportunities. RESULTS. The adolescents who received the AIDS intervention subsequently had greater AIDS knowledge, less favorable attitudes toward risky sexual behavior, and lower intentions to engage in such behavior than did those in the control condition. Follow-up data collected 3 months later revealed that the adolescents who had received the AIDS intervention reported fewer occasions of coitus, fewer coital partners, greater use of condoms, and a lower incidence of heterosexual anal intercourse than did the other adolescents. CONCLUSIONS. These results suggest that interventions that increase knowledge about AIDS and change attitudes toward risky sexual behavior may have salutary effects on Black adolescents' risk of HIV infection.