Objective This study assesses the efficacy and tolerability of fluoxetine in the acute treatment of child and adolescent obsessive-compulsive disorder (OCD) during a 13-week, double-blind, placebo-controlled study. Method Eligible patients aged 7 to 17 (N = 103) were randomized at a ratio of 2:1 to receive either fluoxetine or placebo. Dosing was initiated at 10 mg daily for 2 weeks, then increased to 20 mg daily. After 4 weeks of treatment, and again after 7 weeks of treatment, nonresponders could have their dosage increased by 20 mg daily, for a maximum possible dosage of 60 mg daily. Primary measure of efficacy was improvement in OCD symptoms as measured by the Children's Yale-Brown Obsessive Compulsive Scale (CY-BOCS). All analyses were intent-to-treat. Results Fluoxetine was associated with significantly greater improvement in OCD as assessed by the CY-BOCS (p = .026) and other measures than was placebo. Fluoxetine was well tolerated and had a rate of discontinuation for adverse events similar to that of placebo (p = 1.00). Conclusions Fluoxetine 20 to 60 mg daily was effective and well tolerated for treatment of OCD in this pediatric population.