Rheumatoid arthritis (RA) is often considered a T cell-mediated disease, yet recent studies describe benefit with rituximab, a monoclonal antibody directed against the B cell antigen CD20. We report our experience using rituximab for 5 patients with severe, disease-modifying antirheumatic drug (DMARD)-refractory RA. Five patients with seropositive, erosive RA received rituximab as 4 weekly doses of 375 mg/m. Four subjects experienced remission lasting 5 to 12 months after noting lack of efficacy with antitumor necrosis factor (TNF) therapy. All patients have relapsed, with signs and symptoms of RA returning a mean of 8 months after therapy. Rituximab appears to be a safe and potentially helpful treatment of refractory RA and, until U.S. Food and Drug Administration approval, could be considered for compassionate use in people who have failed multiple DMARDs. Individuals who do not respond to anti-TNF therapy could experience arthritis that is perpetuated by B cell more than T cell function; these patients could be most likely to respond to rituximab. Further studies are needed to clarify the optimal dose and frequency of rituximab therapy, and its role in combination therapy for individuals with RA.