Both behavioral and biomedical interventions are needed to provide education about the health risks associated with unprotected sex and to help those with STIs seek treatment. Communidades Positivas (CPOS) (Spanish for "Positive Communities") is a behavioral intervention designed to reduce the frequency of sexual activity with nonprimary partners. Enhanced partner therapy (EPT) is a biomedical intervention designed to provide treatment to partners who may become or already are infected with an STI and to thereby reduce the rate of reinfections. When implemented individually or together at a community level, these interventions may be effective in preventing HIV/STI transmission in MSM. This study will evaluate the effectiveness of community-level CPOS and EPT, each alone and combined, in reducing sexual risk behavior and HIV/STIs in Peruvian MSM.