Inmates were nominated for the study by selecting every fifth name on the institution's roster. Psychopathy was assessed with the Psychopathy Checklist, and lifetime alcohol and drug disorders were assessed using the National Institute of Mental Health Diagnostic Interview Schedule. The results of co-occurrence analysis clearly indicated that incarcerated psychopaths were at increased risk for lifetime alcohol and drug disorders. In addition, a higher percentage of psychopaths abused multiple drugs when compared with nonpsychopaths. An examination of the relation between substance abuse and factors on the Psychopathy Checklist revealed that substance abuse was significantly related to general social deviance, but was not related to core personality features of psychopathy. Two possible models of psychopathy are presented, unitary syndrome versus dual diathesis models, that may account for the association between psychopathy and substance abuse. 53 references and 5 tables