• Number and percentage of patients with ACR 20/50/70, and mean change from baseline in DAS 28, RAPID, SF-12, FACIT-F, MOS sleep scale. [ Time Frame: Week 24 ] [ Designated as safety issue: No ]
• AEs, laboratory parameters. [ Time Frame: Throughout study ] [ Designated as safety issue: No ]

This 2 arm study will assess the safety and efficacy, with regard to reduction in signs and symptoms, of tocilizumab versus placebo, both in combination with DMARDs, in patients with moderate to severe active rheumatoid arthritis, with an inadequate response to DMARDs. Patients will be randomized in a ratio of 2:1 to receive either tocilizumab 8mg/kg iv or placebo iv every 4 weeks; all patients will also receive stable antirheumatic therapy including permitted DMARDs. The anticipated time on study treatment is 3-12 months, and the target sample size is 500+ individuals.

• Drug: tocilizumab
• Drug: Placebo
• Drug: Permitted DMARDs

Inclusion Criteria:

• adult patients, >=18 years of age;
• active rheumatoid arthritis of >6 months duration;
• receiving permitted DMARDs each at a stable dose for at least 7 weeks prior to baseline.

Exclusion Criteria:

• rheumatic autoimmune disease or inflammatory joint disease other than rheumatoid arthritis;
• major surgery within 8 weeks prior to screening or planned within 6 months following randomization;
• unsuccessful treatment with a biologic agent, including an anti-TNF agent;
• previous treatment with tocilizumab.