This 3 arm study will compare the safety and efficacy, with regard to reduction of signs and symptoms, of tocilizumab versus placebo in combination with methotrexate (MTX) in patients with moderate to severe active rheumatoid arthritis (RA) currently on MTX therapy, and who have had an inadequate response to prior therapy with an anti-tumor necrosis factor (anti-TNF) agent. Patients will be randomized to receive tocilizumab 4mg/kg iv, tocilizumab 8mg/kg or placebo iv, every 4 weeks. All patients will also receive methotrexate 10-25mg/week. The anticipated time on study treatment is 3-12 months, and the target sample size is 500+ individuals.

Inclusion Criteria:

• adult patients at least 18 years of age with moderate to severe active RA for at least 6 months;
• inadequate response to current anti-rheumatic therapies, including MTX;
• inadequate response or intolerance to treatment with 1 or more anti-TNF therapies within 1 year of entering study;
• on stable MTX for at least 8 weeks before entering study;
• patients of reproductive potential must be using reliable methods of contraception.

Exclusion Criteria:

• major surgery (including joint surgery) within 8 weeks before screening, or planned major surgery within 6 months after entering study;
• women who are pregnant or breast-feeding.