The purpose of this study was to estimate the validity of an instrument of the Adolescent Behavioral Classification Project in predicting behavior patterns of emotionally disturbed adolescents in an inpatient setting. Subjects (n = 126) were adolescents admitted to a state residential treatment unit across a period of 35 months. Predictor variables were scores on 17 or 25 factors of the instrument from both adolescents' own responses and their mothers' responses on their behalf. Criterion variables were 10 recreational therapy factors, especially 4 temporally stable factors, and length-of-time in treatment. 3 phases of the project were (I) behavior during initial stages of the therapy, (II) behavioral change after 3 months of therapy, and (III) length-of-time in treatment. In Phase I, both mothers' and adolescents' responses produced significant correlations with criteria; however, in Phase II only the adolescent students' 25 ABCP factors predicted behavioral change. In Phase III, adolescents' responses but not their mothers' responses classified the adolescents by length-of-time in treatment.