A growing body of research shows that personality pathology in adolescents is clinically distinctive and frequently stable into adulthood. A reliable and useful method for rating personality pathology in adolescent patients has the potential to enhance conceptualization, dissemination, and treatment effectiveness. The aim of this study is to examine the clinical validity of a prototype matching approach (derived from the Shedler Westen Assessment Procedure-Adolescent Version) for quantifying personality pathology in an adolescent inpatient sample. Sixty-six adolescent inpatients and their parents or legal guardians completed forms of the Child Behavior Checklist (CBCL) assessing emotional and behavioral problems. Clinical criterion variables including suicide history, substance use, and fights with peers were also assessed. Patients' individual and group therapists on the inpatient unit completed personality prototype ratings. Prototype diagnoses demonstrated substantial reliability (median intraclass correlation coefficient =.75) across independent ratings from individual and group therapists. Personality prototype ratings correlated with the CBCL scales and clinical criterion variables in anticipated and meaningful ways. As seen in prior research with adult samples, prototype personality ratings show clinical validity across independent clinician raters previously unfamiliar with the approach, and they are meaningfully related to clinical symptoms, behavioral problems, and adaptive functioning.