BACKGROUND: Social anxiety disorder is a debilitating, highly prevalent disorder in children and adolescents. If left untreated, it can interfere with emotional, social, and school functioning. OBJECTIVE: To evaluate the efficacy and tolerability of paroxetine in children and adolescents with social anxiety disorder. DESIGN AND SETTING: Multicenter, 16-week, randomized, double-blind, placebo-controlled, flexible-dose, parallel-group, outpatient study. Patients A total of 322 children (8-11 years of age) and adolescents (12-17 years of age) with social anxiety disorder as their predominant psychiatric illness. Intervention Eligible patients were randomized (1:1) to receive paroxetine (10-50 mg/d) or placebo. RESULTS: Four hundred twenty-five patients were screened, and 322 were randomized to treatment. Of these, 319 were included in the intention-to-treat population (paroxetine, n = 163; placebo, n = 156). At the week 16 last observation carried forward end point, the odds of responding (Clinical Global Impression-Improvement score of 1 or 2) were statistically significantly greater for paroxetine (77.6% response [125/161]) than for placebo (38.3% response [59/154]) (adjusted odds ratio, 7.02; 95% confidence interval, 4.07 to 12.11; P<.001). The proportion of patients who were "very much" improved (Clinical Global Impression-Improvement score of 1) was 47.8% (77/161) for paroxetine compared with 14.9% (23/154) for placebo. Adverse events occurring at an incidence of 5% or greater for paroxetine and twice that for placebo were insomnia (14.1% vs 5.8%), decreased appetite (8.0% vs 3.2%), and vomiting (6.7% vs 1.9%). Withdrawals due to adverse events were infrequent (5.5% [9/163] for paroxetine and 1.3% [2/156] for placebo). CONCLUSION: Paroxetine is an effective, generally well-tolerated treatment for pediatric social anxiety disorder.