There is a growing interest in the assessment of adolescent psychopathy to enable early treatment and intervention. Recently, a self-report measure has been developed to assess psychopathic traits in adolescents. The Antisocial Process Screening Device (APSD), a self-report measure of psychopathic traits, and the Psychopathy Checklist: Youth Version (PCL:YV), a clinical rating scale, were administered to a sample of 100 incarcerated male adolescent offenders to assess the concurrent validity of the APSD. Results indicated that the APSD had limited concurrent validity with respect to the PCL:YV and that there appears to be a method effect in the measurement of psychopathy. Thus, it appears the APSD did not assess psychopathy in a manner parallel to that of the PCL:YV. Copyright © 2003 John Wiley & Sons, Ltd.