Prevention of human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS) among adolescents is increasingly recognized as an important public health priority. Sexual risk acts associated with HIV/AIDS transmission (unprotected sexual intercourse with multiple partners of unknown serostatus) are typically initiated by late adolescence, with many youths engaging in sexual relations earlier. Despite being well informed about HIV/AIDS and having positive attitudes toward HIV/AIDS prevention, adolescents have not changed their behavior in response to the pandemic. AIDS-prevention programs must be tailored to consider stereotypic sex roles, gay youths' sexual orientation, and substance abuse. Intensive prevention programs focusing on helping youths perceive HIV as a problem, motivate them to act safely, and implement safe acts by acquiring coping skills, access to condoms and health care, and identifying individual barriers to implementing safe acts have successfully reduced adolescents' risk acts. However, avenues for broad-scale dissemination of such programs or alternative models to change youths' behaviors must be identified.