Rituximab (Rituxan®) is a recombinant chimeric monoclonal antibody that binds to a molecule (CD20) that is present on the surface of B lymphocytes. The product is approved for the treatment of non-Hodgkin's lymphoma and has been investigated for the treatment of a number of autoimmune diseases including rheumatoid arthritis (Edwards 2004) and lupus (Looney 2004, Leandro 2002). As in most rheumatoid arthritis studies, the medication will be administered in this study as a series of two intravenous infusions given 2 weeks apart.