Cleckley, who has given the most extensive and widely supported clinical descriptions of the psychopath, describes the psychopath as a person whose behavior is not explainable in terms of psychosis, neurosis, or mental deficiency. Cleckley lists the salient characteristics of the psychopath as unreliability, insincerity, pathological lying, and egocentricity; poor judgment and impulsivity; a lack of remorse, guilt, or shame; an inability to experience empathy or concern for others, or to maintain warm, affectionate attachments; an impersonal and poorly integrated sex life; and an unstable lifestyle with no long-term commitments. In the authors' three studies reported here, prison inmates were rated on a seven-point scale consistent with Cleckley's conception of psychopathy. Ratings were based on interviews and extensive case-history data. Case histories were used to ascertain convictions for violent crimes and identify agressive and violent behavior both inside and outside of prison. Those offenders classified as psychopaths according to the scale were clearly more aggressive and violent than inmates not so classified. Tabular and graphic data and 26 reference listings are provided.