Case-mix adjustment methods are needed to account for differences between providers when the youth they treat have characteristics that adversely affect treatment success. This study explores variables for adjusting mental health treatment outcomes for adolescents and the differential effects of case-mix adjustment on providers' performance. Linear regression modeling was used to identify case-mix variables for five outcomes. Predictive equations for each outcome were developed for models based on intake clinical data alone, clinical data plus administrative data, and clinical data plus data describing youth history and family environment. Variance explained by intake clinical data alone did not increase appreciably with the addition of administrative data or data describing youth history and family environment. Adjusting outcomes changed the relative performance of certain individual providers substantially, but had a more moderate impact on the overall interpretation of providers' performance.