These three symposium papers summarize the outcomes of studies that explored the accessibility and the utilization of youth mental health services. The first study, "The Role of Diagnostic Systems" (Theodore Fallon and Mary Schwab-Stone), involving 219 children (ages 6-12), examined the perils involved in the use of categorical diagnosis to identify who is in need of care. It found that depending on who was queried and how the information from the informants was combined, anywhere from 3 to 62 percent of the children could be diagnosed as having attention deficit hyperactivity disorder. The second study, "The Role of Economics and Jails: Access and Outcome for Under-Served Youth" (Andres J. Pumariega), compared mental health treatment of school-based youth, incarcerated youth, and a community mental health treatment group, to illustrate that entire populations can be overlooked when considering who needs care. Results found that youth from low socio-economic populations are under served in mental health programs. The third study, "A Longitudinal Study of Adolescent Mental Health Service Use" (Cuffe, Jackson, Waller, Chilappagari, Garrison, Addy, and McKeown), reports on mental health service use data from a longitudinal, school-based epidemiologic study of adolescent depression. Results found that most of the adolescents with psychiatric disorders failed to receive treatment, and that there are significant differences in both service use and perceived barriers to services by race and gender. (CR)