The main objective of this work was to provide an updated review of the efficacy of behavioral interventions to reduce sexual risk of HIV among adolescents. We searched electronic databases, leading public health journals, and the document depository held by the Synthesis of HIV/AIDS Risk Reduction Project. Studies that fulfilled the selection criteria and were available as of December 31, 2008 were included. Studies were included if they investigated any behavioral intervention advocating sexual risk reduction for HIV prevention, sampled adolescents (age range, 11-19 years), measured a behavioral outcome relevant to sexual risk, and provided sufficient information to calculate effect sizes. Data from 67 studies and 98 interventions (N = 51,240 participants) were included. Independent raters coded participant and intervention characteristics as well as methodological features. Weighted mean effect sizes, using both fixedand random-effects models, were calculated; positive effect sizes indicated greater risk reduction.