Psychopathy traditionally is defined by a cluster of inferred personality traits and socially deviant behaviors. The accepted standard for the reliable and valid assessment of psychopathy is the Psychopathy Checklist-Revised (PCL-R). Because of its importance in basic and applied research, and in the mental health and criminal justice systems, the PCL-R has been subjected to intense scrutiny by researchers and clinicians. In this article we discuss issues surrounding its structural properties and those of its derivatives. Using factor analysis, item response theory, and multidimensional scaling, we propose that the PCL-R and its derivatives are underpinned by at least four correlated factors: Interpersonal, Affective, Lifestyle, and Antisocial. We argue that attempts to characterize antisocial behaviors as merely "downstream" manifestations of more central traits are inconsistent with the structural properties of the PCL-R and with evidence that the development of traits and actions are interactive and reciprocal. We also report new evidence that psychopathy and its factors are dimensional in nature, perhaps extreme variants of normal personality traits and behaviors.