Participants were 1146 male offenders incarcerated in state prisons (n=569), or court-ordered to residential drug treatment (n=577). Participants were interviewed using the Structured Clinical Interview for DSM-IV Axis II Personality Disorders (SCID-II) to assess ASPD symptoms; they also completed the Personality Diagnostic Questionnaire-4 (PDQ-4) ASPD scale. Taxometric analyses were performed to examine whether ASPD is underpinned by a discrete category or a dimensional construct.