We examined the association between perceptions about condom use among one's peers, beliefs about new HIV treatments, and HIV sexual risk behaviour among 849 young African-American men who have sex with men (MSM). Participants were randomly recruited from and anonymously interviewed in community venues in Atlanta, Georgia, USA, in cross-sectional samples between 1999 and 2002. Data analyses indicated that 30% of the sample reported unprotected anal intercourse in the past three months; stronger peer condom norms predicted less-frequent risky sexual behaviour. However, the belief in less threat of HIV because of HIV treatments was not associated with either risky sexual behaviour or peer norms, and peer norms did not mediate the association between HIV treatment beliefs and unprotected anal intercourse. These findings suggest that changing peer norms for condom use may reduce HIV risky sex in African-American MSM, regardless of their beliefs about HIV drug treatments.