Objective: As awareness of the high prevalence of mental health problems among juvenile offenders has grown, researchers and practitioners have recognized the need for reliable and efficient methods of assessing such problems among large numbers of offenders to ensure that limited treatment resources are applied to those with the greatest need. Method: Between May 2000 and October 2002, 18,607 admissions were administered the computerized version of the Massachusetts Youth Screening Instrument Version 2 (MAYSI-2) 24 to 48 hours after their arrival at detention centers throughout Pennsylvania. Results: Approximately 70% of the males and 81% of the females scored above the clinical cutoff on at least one of the following five MAYSI-2 scales: Alcohol/Drug Use, Angry-Irritable, Depressed-Anxious, Somatic Complaints, and/or Suicide Ideation. Girls were more likely than boys to exhibit internalizing as well as externalizing problems. Mental health problems were most prevalent among white youths and least prevalent among African American youths. When youths repeated the screen upon subsequent visits to detention, their scores generally remained stable. Conclusions: The findings suggest that the MAYSI-2 is a promising triage tool for emergent risk. The use of such a screen may reduce bias in allocation of treatment resources and improves our understanding of the nature of mental health problems in delinquent populations.