This article provides a comprehensive review of research on the effects of behavioral interventions on heterosexual adolescents' HIV sexual-risk behavior. It details adolescents' risk of sexually transmitted HIV infection and describes challenges associated with adolescent intervention research, including obtaining school and parent approval and the validity of self-reported measures. It describes central characteristics of 36 controlled intervention studies assessing the HIV sexual-risk behavior of over 30,000 male and female adolescents 11-21 years of age. It summarizes the participants' race/ethnicity and age, the theoretical framework, and the intervention setting, duration and outcome. This review reveals that the most commonly assessed behavioral outcomes were condom use and abstinence, and the largest effects sized were on condom use and condom acquisition. Effect sizes for abstinence and number of sexual partners were the smallest. Perceived self-efficacy and behavioral interventions were the most commonly assessed theoretical mediators. Key questions this research engaged in included whether behavioral skills can be increased, whether intervention-induced behavior change can be sustained, whether matching the race/ethnicity and gender of facilitators and participants enhances the effectiveness of culturally sensitive interventions, whether classroom teachers can effectively facilitate interventions, whether the behavior of high-risk populations can be changed, and which kinds of interventions are most effective. This review concludes that carefully designed theory-based interventions that take into account the characteristics of the particular population or culture can cause positive changes in adolescents' HIV sexual-risk behavior, but boundary conditions for their effectiveness still need to be identified. Several suggestions for additional research are proffered.