Community epidemiological data on the prevalence and correlates of adolescent mental disorders are needed for policy planning purposes. Only limited data of this sort are available. To present estimates of 12-month and 30-day prevalence, persistence (12-month prevalence among lifetime cases and 30-day prevalence among 12-month cases), and sociodemographic correlates of commonly occurring DSM-IV disorders among adolescents in the National Comorbidity Survey Replication Adolescent Supplement. The National Comorbidity Survey Replication Adolescent Supplement is a US national survey of DSM-IV anxiety, mood, behavior, and substance disorders among US adolescents based on face-to-face interviews in the homes of respondents with supplemental parent questionnaires. Dual-frame household and school samples of US adolescents. A total of 10,148 adolescents aged 13 to 17 years (interviews) and 1 parent of each adolescent (questionnaires). The DSM-IV disorders assessed with the World Health Organization Composite International Diagnostic Interview and validated with blinded clinical interviews based on the Schedule for Affective Disorders and Schizophrenia for School-Age Children. Good concordance (area under the receiver operating characteristic curve ≥0.80) was found between Composite International Diagnostic Interview and Schedule for Affective Disorders and Schizophrenia for School-Age Children diagnoses. The prevalence estimates of any DSM-IV disorder are 40.3% at 12 months (79.5% of lifetime cases) and 23.4% at 30 days (57.9% of 12-month cases). Anxiety disorders are the most common class of disorders, followed by behavior, mood, and substance disorders. Although relative disorder prevalence is quite stable over time, 30-day to 12-month prevalence ratios are higher for anxiety and behavior disorders than mood or substance disorders, suggesting that the former are more chronic than the latter. The 30-day to 12-month prevalence ratios are generally lower than the 12-month to lifetime ratios, suggesting that disorder persistence is due more to episode recurrence than to chronicity. Sociodemographic correlates are largely consistent with previous studies. Among US adolescents, DSM-IV disorders are highly prevalent and persistent. Persistence is higher for adolescents than among adults and appears to be due more to recurrence than chronicity of child-adolescent onset disorders.