Etanercept has been recently approved in the United States for the treatment of moderate to severe plaque psoriasis in patients aged 4-17 years. The objective of this study was to characterize etanercept pharmacokinetics, immunogenicity, and efficacy in pediatric patients. Data from a phase 3 study and open-label extension study were analyzed. Etanercept serum concentrations in pediatric patients receiving etanercept 0.8 mg/kg (maximum, 50 mg) weekly were compared with adult psoriasis patients and pediatric patients with juvenile idiopathic arthritis (JIA) who received etanercept 0.4 mg/kg twice weekly. The developments of antietanercept antibodies and efficacy based on the Psoriasis Area and Severity Index were evaluated. Steady-state trough etanercept concentrations were similar across visits from weeks 12-48, between patients aged 4-11 and 12-17 years, between pediatric and adult psoriasis patients, and between pediatric patients with psoriasis or JIA. Etanercept serum concentrations and safety profiles were similar in patients with (15.9%) and without antietanercept antibodies. Dosing used in the study provided similar exposures and efficacy across ranges of weight and body mass index. Pharmacokinetic, immunogenicity, and efficacy data support 0.8 mg/kg (maximum, 50 mg) weekly dosing of etanercept in patients aged 4-17 years.