The most salient clinical characteristics of psychopaths include unreliability, insincerity, egocentricity, poor judgment, impulsivity, interpersonal difficulties, and an inability to experience guilt or empathy. Assessment procedures used in diagnosis include global clinical impressions, rating scales, self-report inventories, and checklists. In general, clinical-behavioral assessment procedures appear to be the most reliable. Depending on diagnostic criteria, it is estimated that 15 to 25 percent of male incarcerates meet relatively stringent criteria for psychopathy. Compared to nonpsychopathic offenders, psychopathic offenders began their criminal careers earlier and committed more offenses, but were just as likely to be paroled. In addition, psychopathic offenders' crimes were more aggressive and violent, and psychopaths were more likely to be involved in violent behaviors while incarcerated. Finally, psychopathic offenders are more likely than others to violate the terms of conditional release. 10 tables, 6 figures, and 41 references.