Although impulsivity is likely to be related to HIV risk--particularly in incarcerated substance-abusing youth--this area of research has been understudied. To investigate the relationship between impulsivity and various HIV/AIDS risk behaviors and attitudes, a sample of court-referred and incarcerated culturally diverse inner-city adolescents (males: N = 266; females: N = 111) were divided into high and low impulsive groups based on the Millon Adolescent Clinical Inventory Impulsivity Scale. Findings showed that compared to the less impulsive group, the highly impulsive adolescents reported more frequent marijuana and alcohol use in the last 3 months as well as a significantly higher proportion of unprotected sex when high on alcohol and marijuana, higher perceived susceptibility to HIV, more AIDS-related anxiety, greater HIV knowledge, less sexual self-efficacy, and less favorable sexual attitudes. Implications for interventions among incarcerated youth are discussed.