Background: Anxiety disorders are often undetected and untreated in adolescents. This study evaluates the relative efficacy of a school-based, cognitive-behavioral intervention compared to an educational-supportive treatment for adolescents with social anxiety disorder. Methods: Thirty-six students (30 females), ages 14 to 16, were randomized to a 12-week specific intervention, Skills for Social and Academic Success (SASS), or a credible attention control matched for structure and contact, conducted in school. Results: Independent evaluations and adolescent self-reports indicated significant reduction in social anxiety for SASS compared to the control group. Parent reports of their children's social anxiety did not discriminate between treatments. In the specific intervention, 59%, compared to 0% in the control, no longer met criteria for social anxiety disorder following treatment. Superiority of the SASS intervention was maintained 6 months after treatment cessation. Conclusions: The study provides evidence that intervention for social anxiety disorder that emphasizes exposure and social skills is efficacious. Results indicate that clinical improvement is sustained for at least 6 months, and that, overall, adolescents with social anxiety disorder do not respond to non-specific treatment. This investigation has public health implications by demonstrating that effective interventions can be transported to nonclinical settings.