Most opiate users are injection drug users (IDUs). A significant percentage of IDUs have antisocial personality disorder (APD). APD has been found by some researchers to be an additional risk factor for human immunodeficiency virus (HIV) infection in IDUs. The present study evaluated the association of sociodemographic characteristics, substance abuse history, and several measures of antisociality including the DSM-III-R diagnosis made by the Personality Disorder Examination, the California Psychological Inventory-Socialization Scale, and Hare's Revised Psychopathy Checklist, to behaviors associated with HIV risk in 289 opiate-dependent methadone-maintained subjects. The presence of drug- and sex-related risky behaviors measured by the Risk Assessment Battery was predicted more consistently by measures of personality traits associated with antisociality than by a diagnosis of APD.