Objective: To determine whether adopted adolescents are at excess risk for clinically relevant behavioral and emotional problems. Design: We examined whether adopted and non-adopted adolescents differed on quantitative indicators of mental health and the prevalence of childhood disorders and whether differences exist between internationally and domestically placed adoptees. Setting: Assessments occurred at the University of Minnesota from December 11, 1998, to June 4, 2004. Participants: Adolescents adopted in infancy were systematically ascertained from records of 3 large Minnesota adoption agencies; nonadopted adolescents were ascertained from Minnesota birth records. The final sample included these adolescents with their rearing parents. Main Exposure: The main exposure was adoptive status: nonadopted (n=540), international adoptive placement (n=514), or domestic adoptive placement (n=178). Outcome Measures: Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) clinical assessments based on child and parent reports of attention-deficit/ hyperactivity, oppositional defiant, conduct, major depressive, and separation anxiety disorders; teacher reports of psychological health; and contact with mental health professionals. Results: Adoptees scored only moderately higher than nonadoptees on quantitative measures of mental health. Nevertheless, being adopted approximately doubled the odds of having contact with a mental health professional (odds ratio [OR], 2.05; 95% confidence interval [CI], 1.48-2.84) and of having a disruptive behavior disorder (OR, 2.34; 95% CI, 1.72-3.19). Relative to international adoptees, domestic adoptees had higher odds of having an externalizing disorder (OR, 2.60; 95% CI, 1.67-4.04). Conclusions: Moderate mean differences in quantitative indicators of mental health can lead to substantial differences in disorder prevalence. Although most adopted adolescents are psychologically healthy, they may be at elevated risk for some externalizing disorders, especially among those domestically placed.