This article presents the results of a systematic review of the effectiveness and economic efficiency of individual-, group-, and community-level behavioral interventions intended to reduce the risk of acquiring sexually transmitted HIV in adult men who have sex with men (MSM). These results form the basis for recommendations by the Task Force on Community Preventive Services on the use of these interventions. Sexual risk behavior and condom use were the outcomes used to assess effectiveness. Intervention effectiveness on biological outcomes could not be assessed because too few studies of adequate quality have been published. The evidence found in our review shows that individual-level, group-level, and community-level HIV behavioral interventions are effective in reducing the odds of unprotected anal intercourse (range 27% to 43% decrease) and increasing the odds of condom use for the group-level approach (by 81%). The Task Force concluded that the findings are applicable to MSM aged 20 years or older, across a range of settings and populations, assuming that interventions are appropriately adapted to the needs and characteristics of the MSM population of interest. Based on findings from economic evaluation studies, the Task Force also concluded that group- and community-level HIV behavioral interventions for adult MSM are not only cost effective but also result in actual cost savings. Additional information about other effects, barriers to implementation, and research gaps is provided in this paper. The recommendations based on these systematic reviews are expected to serve the needs of researchers, planners, and other public health decision makers.