The research scale for psychopathy developed by Hare (1980) represents an important recent advance in the assessment of this disorder in that it emphasizes objectivity and reliability. This study compares the factor structure of the scale derived from an English prison sample with the original Canadian sample in order to assess the cross-cultural generalizability of the checklist and reassess the factorial basis of the scale. Results from the first analysis indicate substantial correspondence between psychopathy factors derived from English and Canadian analyses. Results of a second analysis suggest that four main clusters of traits (emotional detachment, superficial relationships, egocentricity, and impulsivity) are centrally important in the identification of psychopathy. Results of further psychometric analyses suggest increasing the scale's validity by deleting several items having little in common with the main features of psychopathy. It is concluded that Hare's checklist is both applicable to an English population and internally valid, and that future research may usefully investigate correlates of each of the four psychopathy factors.