The author presents data on the incidence and reliability of the DSM-III diagnosis of antisocial personality disorder in 246 male inmates of two prisons, comparing this diagnosis with assessment procedures that have proven useful in the study of psychopathy. He found good agreement between the diagnosis of antisocial personality disorder and assessments of psychopathy, although DSM-III did not readily identify individuals who fit the classic picture of psychopathy but avoided early contact with the judicial system. Nevertheless, DSM-III may be useful for differential diagnosis in criminal populations.