This study was designed to examine the impact of HIV treatment optimism on sexual risk among a racially diverse sample of HIV-positive MSM. Survey data were collected from 346 racially diverse HIV-positive MSM. Inclusion criteria: 18 years of age, male, at least one incident of unprotected anal intercourse (UAI) in the last year, currently on treatment. Other variables included demographics, sexual risk, depression, internalized homonegativity, HIV treatment history, alcohol/drug use and beliefs about HIV treatments (Susceptibility to transmit HIV, Severity of HIV infection and Condom Motivation). Those with lower income were more likely to report that HIV was less transmissible. A self-reported decrease in condom motivation was associated with being White, well-educated and increased alcohol/drug use. A decrease in Severity of HIV was associated with better mental health, being non-White and undetectable viral load. Sexual risk appears related to beliefs about how treatment affects the transmissibility of HIV. Race, socioeconomic status, alcohol/drug use, mental health and viral load were also associated with treatment beliefs.