Objective: To examine the 12-month prevalence of psychotropic medication use among adolescents, and the match between mental disorder diagnoses and past-year antidepressant and stimulant use. Method: Data are from the National Comorbidity Survey--Adolescent Supplement (2002-2004), a nationally representative survey of 10,123 adolescents aged 13 to 18 years that assesses "DSM-IV" disorders using a fully structured diagnostic interview, a modified version of the World Health Organization Composite International Diagnostic Interview (CIDI). Rates of 12-month psychotropic medication use are stratified by respondent socio-demographic characteristics, and the distribution of 12-month "DSM-IV" CIDI disorders is estimated among past-12-month use of antidepressants and stimulants. Results: During a 1-year period, 7.0% of adolescents used at least one psychotropic medication; these medications were most commonly antidepressants (3.9%), followed by stimulants (2.8%), anxiolytics (0.8%), antipsychotics (0.5%), and mood stabilizers (0.4%). Nearly three-quarters (74.1%) of adolescents with any past-year psychotropic medication use had at least one CIDI mental disorder, and many had disorders for which the specific medication class is clinically indicated. Among adolescents using antidepressants, 48.8% had a past-12-month depressive or anxiety disorder, and an additional 20.3% had a lifetime depressive or anxiety disorder. Nearly one-half (49.1%) of adolescents using stimulants met past-12-month attention-deficit/hyperactivity disorder (ADHD) criteria, and an additional 13.1% met lifetime criteria for ADHD. Conclusions: Most adolescents who are treated with psychotropic medications have one or more psychiatric disorders and many, albeit far from all, have mental disorders for which the specific medications are clinically indicated. (Contains 4 tables.)