This study examined the prevalence of and associations between specific psychiatric disorders, substance use problems, and trauma exposure in a sample of delinquent and nondelinquent adolescents. A nationally representative sample of adolescents ("n" = 3,614; "M" age = 14.5 years, "SD" = 1.7; 51% male; 71% White, non-Hispanic, 13.3% African American, non-Hispanic, 10.7% Hispanic) was interviewed via telephone about engagement in delinquent acts and their experience of posttraumatic stress disorder, major depressive episode, substance use, interpersonal violence, and other forms of trauma exposure. Delinquent adolescents were more likely than nondelinquent adolescents to experience trauma; they were also more likely to report past-year posttraumatic stress disorder, major depressive episode, alcohol abuse, and nonexperimental drug use. After accounting for the effects of demographics and trauma exposure, delinquency was associated with increased likelihood of posttraumatic stress disorder and problematic substance use in both genders and increased likelihood of major depressive episode in girls. Findings highlight substantial overlap among delinquency, trauma exposure, posttraumatic stress disorder, and major depressive episode in adolescents and the need for interventions that address these varied clinical problems. Future work should examine the factors underlying the development of these relations over time. (Contains 3 tables, 1 figure, and 1 footnote.)