Social network composition is known to effect patterns of reported sexual risk-taking among men who have sex with men (MSM); however, consensus as to the directionality and size of these effects is lacking. We examined the relationships between novel aspects of social network composition and sexual risk-taking using a cross-sectional survey of 870 MSM. Social network composition was found to have mixed effects on reported sexual risk-taking: reporting proportionally more lesbian, gay, or bisexual (LGB)-identified friends and reporting friends who were on average significantly older than the respondent were both associated with reporting increased sexual risk, while reporting proportionally more LGB-identified friends in relationships and reporting a social network proportionally more aware of the respondent's homosexuality/bisexuality were both associated with reporting decreased sexual risk. The support structures created by differing social network compositions-and particularly the presence of LGB couples-may be a potential area for targeting sexual risk-reduction interventions for MSM.