Assessing mental health problems ensures that limited treatment resources are applied to those with the greatest need. 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 15 detention centers throughout Pennsylvania. The MAYSI-2 was designed to assist juvenile justice facilities in identifying youths that may have special mental health needs. About 70 percent of the males and 81 percent 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. While older youths were more likely to present with alcohol/drug use problems and traumatic experiences, younger youths were more likely to present with anger-irritable symptoms as well as depressed-anxious moods. The results indicate that the MAYSI-2 is a promising triage tool for emergent risk. 1 figure, 4 tables, 30 references