This document focuses on adolescent depression, described as a major, pervasive, and perhaps increasing problem. A brief introduction to depression in adolescence, with case examples, is followed by a discussion of what constitutes adolescent depression. Depressed mood, depressive syndromes, and clinical depression are three approaches taken in the field. An integration of these three approaches to adolescent depression is presented. A discussion of who becomes depressed in adolescence looks again at the three approaches to depression and examines variations by gender, group, and cohort. Extensive tables are provided which compare studies assessing depressed affect and studies assessing symptoms related to depression. Related disorders and problems are considered. A section on developmental processes explores both risk and protective factors, concentrating on the areas of biological processes, psychological factors, cognitive factors, family factors, peers, school factors, daily stress and stressful life events, and developmental trajectories. A section on approaches to intervention focuses on the treatment of adolescent depression, prevention of adolescent depression, and an integration of treatment and prevention efforts. A final section looks at implications for research, program, and national policy. Contains approximately 125 references and 7 tables. (NB)