Treatment of severe juvenile idiopathic arthritis (JIA) represents a serious challenge. This study investigates the efficacy and safety of repeat courses of rituximab in patients with different forms of JIA refractory to infliximab and standard immunosuppressive therapy. Patients (n = 55; age 2.3-17.0 years) with severe polyarticular and systemic JIA (International League of Association for Rheumatology diagnostic criteria) received rituximab (one intravenous infusion/week for 4 weeks, 375 mg/m(2) per dose). Efficacy was assessed using the American College of Rheumatology Pediatric (ACR Pedi) criteria. The primary endpoint was an ACR Pedi 30 response at week 24. At week 24, ACR Pedi 30, 50, and 70 responses were achieved by 98%, 50%, and 40% of patients, respectively. By week 96, ACR Pedi 30, 50, and 70 responses were achieved by 98%, 93%, and 93% of 25 patients, respectively. Remission was recorded in 25%, 52%, 75%, and 98% of patients following the first (24 weeks), second (48 weeks), third (72 weeks), and fourth (96 weeks) courses of rituximab, respectively. Rituximab treatment significantly reduced the number of systemic manifestations at week 12 and also enabled 52% of patients to achieve remission of arthritis by week 48. This study supports the efficacy of rituximab in patients with severe forms of JIA, refractory to several prior agents.