In response to PA-97-066 and PA-99-131, the proposed project will develop descriptive information and test hypotheses regarding population characteristics, service use, and service outcomes of youth with co-occurring disorders. Previously collected data from three large- scale research projects about child and adolescent behavioral health services will be reanalyzed as a cost-effective way of obtaining additional insights into the needs and experiences of this population. These existing data sets provide comprehensive youth, family, and service use information. Each data set includes administrative data (with encounter or claims data with diagnostic, services, and provider information) and interview data (with comprehensive youth, family, and service data for approximately 1000 adolescents with documented alcohol use and mental health problems). As part of the hypothesis testing, models of service utilization and outcomes for youth with co- occurring alcohol-related and mental disorders will be developed and tested. Individual, familial, community, and service system factors that affect service access and use will be examined, based on a theoretical framework. In additional, sources of variation in access and service use will be examined for multiple cohorts, including youth of different genders and different racial groups. The project builds on program of health services research by the Principal Investigator that has focused on child, adolescent, and family behavioral health issues.