This study examines longitudinal mental health service use patterns of a school-based sample of adolescents. Based on the Center for Epidemiologic Studies Depression Scale scores, a stratified sample of middle-school students was interviewed using the Schedule for Affective Disorders & Schizophrenia for School-Aged Children. Service use decreased over time. Under-treatment of youth with psychiatric diagnoses was found to be a significant problem, with differences in service use by race & gender over time. (26 refs)