 This study will evaluate the efficacy and safety of ocrelizumab, compared with placebo, in combination with methotrexate in patients with active rheumatoid arthritis who have had an inadequate response to methotrexate. Patients will be randomized to receive placebo, 200mg of intravenous ocrelizumab or 500mg of i.v. ocrelizumab on Days 1 and 15. A repeat course of i.v. treatment will be administered at Weeks 24 and 26. All patients will receive 7.5mg - 25mgweek concomitant methotrexate at a stable dose. The anticipated time on study treatment is 1-2 years. Target sample size is 1000. 