As a result of Kansas v Hendricks, many sex offenders in the U.S. are likely to be civilly committed to mental institutions for indefinite periods, and many others with histories of violent offenses may also be so committed. It therefore becomes critical for mental health professionals to understand the risk factors for re-offending that put the public in jeopardy. The most reliable of these factors is psychopathy, which will here be defined, along with its differentiation from the more commonly diagnosed antisocial personality disorder. The assessment of psychopathy, its relationship to crime--especially, to violent crime, its (non-) responsiveness to the usual treatment, and an outline of a potentially more effective one, are presented. Finally, and particularly in view of its widely accepted validity, the potential for abuse of the PCL-R and :SV are noted.