There are reports of increased sexual risk behavior among people on highly active antiretroviral therapy (HAART) due to beliefs about risk of HIV transmission when on HAART. In a cross-sectional study (Seropositive Urban Men's Study), we examined the relationship between risk perception and sexual risk behavior among sexually active, culturally diverse HIV positive men who have sex with men (N = 456). Less than twenty-five percent engaged in unprotected anal sex (either with an HIV negative, or unknown-status partner, or an HIV positive partner) within the past 3 months. Most men believed there was significant health risk (to partner or self) associated with unprotected sex when on HAART. There was no increased risk behavior associated with being on HAART, although the perception of negative health consequences, including HIV transmission, when on HAART was significantly lower for the relatively small subset of men who reported unprotected sex. Prevention strategies need to be tailored to address risk perception associated with HAART.