B cells play an important role in the pathogenesis of many autoimmune diseases. Selective targeting of these cells has been recently achieved using a chimeric monoclonal antibody against the pan B cell surface marker CD20 (rituximab). This antibody was originally developed for the treatment of non-Hodgkin's lymphoma. It was found to be effective, well tolerated and had a very good safety profile. Recent studies have demonstrated the efficacy of rituximab in several refractory autoimmune disorders including rheumatoid arthritis, systemic lupus erythematosus, immune thrombocytopenic purpura, chronic cold agglutinin disease, IgM-mediated neuropathies and mixed cryoglobulinemia.