The present study was designed to determine the utility of pretreatment data in predicting completion and dropout from adolescent substance abuse treatment. One hundred thirty two consecutively admitted adolescents (mean age=16.4 years; 93 male subjects, 39 female subjects) with significant substance abuse were administered a battery of standardized substance abuse, psychopathology, and social questionnaires immediately after admission to an intensive, set-length substance abuse treatment program. Seventy-four adolescents completed the program. Using discriminant function analyses, five pretreatment measures were found to predict treatment completion in male subjects, including: greater severity of problems with alcohol; greater use of drugs other than alcohol, cannabis, and tobacco; higher degree of internalizing problems; and lower self-esteem. Significant predictors for completion by female subjects were not found. The role of treatment readiness and motivation for male subjects is examined, and the lack of significant findings for female subjects is discussed.