Rituximab (anti-CD20) is a man-made antibody used to treat certain types of cancer. The drug blocks the CD20 antigen found on the surface of B cells and is known to deplete B cells when administered intravenously. Previous research suggests B-cell activity is important in pathogenesis of RA, so B-cell depletion may decrease inflammation and other symptoms of RA. Rituximab has recently been approved by the FDA for use in combination with MTX for treatment of patients with moderately to severely active RA who have had an inadequate response to TNF-blocking agents. This study will examine the effects of rituximab on the immune response and disease activity in patients with early active RA who have not been treated with any disease-modifying agent. Levels of B and T cells and other markers of disease activity will be monitored during the study. The safety and tolerability of rituximab in this DMARD-naive population will be examined.