Objective: To evaluate the safety, tolerability, and clinical effects of rituximab, an anti-CD20 monoclonal antibody, in the treatment of severe pediatric autoimmune diseases. Study design: We reviewed the records of 10 patients treated with rituximab for severe, refractory autoimmune diseases at a single tertiary care children's hospital. Adverse events as well as treatment effects were recorded. Results: All patients received 4 weekly doses of rituximab at 375 mg/m2 per dose. One patient died as the result of complications of her underlying systemic lupus erythematosus 7 weeks after rituximab therapy. Three patients had serious infections, all of which resolved with standard therapy. Rituximab led to transient or sustained improvement in clinical and laboratory parameters in nine subjects. At a median follow-up of 9 months, the median prednisone dose was reduced in the responders by 0.75 mg/kg per day (mean decrease of 63%), and four patients were able to discontinue corticosteroids entirely. With longer follow-up (median, 22 months), we found that 5 of 9 patients remained clinically stable after rituximab therapy, whereas 4 patients had recurrent or new features of their underlying autoimmune disorders requiring additional corticosteroids or other immunosuppressive medications. Conclusions: Rituximab had an acceptable toxicity profile in this group of patients with severe, refractory autoimmune diseases, although there were three serious infections and one patient death. Rituximab appears to be beneficial for patients with refractory autoimmune diseases and may reduce corticosteroid exposure. Although rituximab therapy provided a durable clinical benefit for some patients in this population, other patients had reemergence of their underlying autoimmune disease.