A Phase II study (WA16291) has been completed in patients with rheumatoid arthritis (RA) . A total of 161 patients were randomized to 4 treatment arms: Methotrexate, Rituximab alone, Rituximab and Methotrexate, Rituximab and Cyclophosphamide. Two doses of Rituximab, 1 gm each, were administered IV two weeks apart. Infusion reactions were observed in 36% of patients during their first infusion of Rituximab compared to 30% for placebo . Four Rituximab-treated patients developed serious infections, for a rate of 4.6 per 100 patient years. For context, the rate of infections requiring hospital admission was 9.57 per 100 patient years in a community based epidemiologic study in RA.