This study will evaluate the efficacy and safety of MabThera in patients with active rheumatoid arthritis who have had an inadequate response to one prior anti-TNF alpha inhibitor. MabThera-naive patients will be stratified into 3 arms, according to previous inadequate response to a)etanercept, b)infliximab or c)adalimumab. Patients will be treated with MabThera (1g infusion) on day 1 and day 15, and will continue their basic methotrexate therapy. The anticipated time on study treatment is 2+ years, and the target sample size is 100-500 individuals.