In a community study of 386 Caucasian working-class older adolescents, a sizeable proportion met lifetime criteria for selected DSM-III-R diagnoses. Alcohol abuse/dependence had the highest lifetime prevalence rate (32.4%), followed by phobias (22.8%), drug abuse/dependence (9.8%), major depression (9.4%), and, least commonly, post-traumatic stress disorder (6.3%) and obsessive compulsive disorder (2.1%). Significant gender differences were found for major depression, post-traumatic stress disorder, and alcohol abuse/dependence, whereas socioeconomic differences occurred in major depression, phobias, and drug abuse/dependence. Adolescents with specific psychiatric disorders had significantly poorer functioning on measures of behavioral problems, interpersonal problems, self-esteem, and school performance. Results suggest the importance of identifying psychiatric disorder in adolescence, and the need for preventive strategies and prompt treatment.