BACKGROUND: Safe and effective therapies are needed for pediatric patients with psoriasis. OBJECTIVE: The purpose of this study was to evaluate ustekinumab in patients age 12 to 17 years who had moderate-to-severe psoriasis. METHODS: Patients (n = 110) were randomly assigned to ustekinumab standard dosing (SD; 0.75 mg/kg [=60 kg], 45 mg [>60-=100 kg], and 90 mg [>100 kg]) or half-standard dosing (HSD; 0.375 mg/kg [=60 kg], 22.5 mg [>60-=100 kg], and 45 mg [>100 kg]) at weeks 0 and 4 and every 12 weeks or placebo at weeks 0 and 4 with crossover to ustekinumab SD or HSD at week 12. Clinical assessments included the proportion of patients achieving a Physician's Global Assessment of cleared/minimal (PGA 0/1), at least 75% improvement in Psoriasis Area and Severity Index (PASI 75), and at least 90% in PASI (PASI 90). Adverse events (AEs) were monitored through week 60. RESULTS: At week 12, 67.6% and 69.4% of patients receiving ustekinumab HSD and SD, respectively, achieved PGA 0/1 versus 5.4% for placebo (P < .001). Significantly greater proportions receiving ustekinumab achieved PASI 75 (HSD, 78.4%; SD, 80.6%; placebo, 10.8%) or PASI 90 (HSD, 54.1%; SD, 61.1%; placebo, 5.4%) at week 12 (P < .001). Through week 12, 56.8% of placebo patients, 51.4% of HSD patients, and 44.4% of SD patients reported at least one AE; through week 60, 81.8% reported AEs. LIMITATIONS: The study was small relative to adult trials. CONCLUSIONS: In this patient population (12-17 years), the standard ustekinumab dose provided response comparable to that in adults with no unexpected AEs through 1 year.