The reliability and validity of the State-Trait Anxiety Inventory for Children (STAIC) was studied with 675 adolescents aged 12 to 18 recruited from clinical and community sources. The STAIC is a self-report measure that has been widely used to assess state and trait anxiety of children. It has been suggested that the child version may be more useful with adolescent populations than the adult version. A three-factor solution fit the data better than a two-factor solution. The correlations between factor loadings and item response theory (IRT) slopes ranged between 0.95 and 0.98, and all of the items of the STAIC were highly discriminating. Scores from factor loadings, scores from the IRT slopes, and summary scores discriminated the groups with or without an anxiety disorder. Results from the confirmatory factor analysis and reliability study indicated that the STAIC was applicable to adolescents. (Contains 2 tables and 14 references.) (Author/SLD)