The paper describes structural and HIV-related network characteristics and examines associations between these various social network domains and HIV risk behaviors among a sample of 356 men randomly selected from a methadone maintenance treatment program (MMTP) in New York City. Multiple logistic regression analyses suggest that (1) a higher level of perceived sexual risk among network members, referred to as "alters" in this study, was associated with an increased likelihood of the participant engaging in sexual risk behaviors; (2) participants who indicated that they exchanged encouragement with a higher number of network alters about using condoms were less likely to report engaging in unprotected sex; and (3) participants who indicated that they talked about HIV risks with a higher number of network alters were less likely to engage in unprotected sex in the past 6 months. Collectively, these findings support the notion that networks may influence the adoption of risk reduction strategies in this population. Implications of the findings for HIV prevention network interventions for men in MMTPs are discussed.