Used psychosocial variables derived from the health belief model (Rosenstock, 1974), Bandura's (1986) self-efficacy framework, and protection motivation theory (Rogers, 1984) to predict self-reported AIDS risk-reduction behaviors in a sample of 389 homosexual men who participated in the Multicenter AIDS Cohort Study in Los Angeles and who knew their HIV antibody status. Hierarchical multiple regression analyses showed that self-efficacy, perceived risk, response efficacy, and prior sexual behavior accounted for approximately 70% of the variance in the total number of sexual partners and the number of anonymous partners over a 6-month interval, controlling for demographic variables, HIV antibody status, and presence of a primary partner. A logistic regression analysis showed that barriers to change predicted increased unprotected anal receptive intercourse over a 6-month interval, controlling for prior behavior. The relation of health beliefs to risk-reduction behavior was substantially different for HIV-seropositive men without primary partners than for other groups of gay men. Implications for interventions are discussed.