This 3-part study evaluated the efficacy and safety of tocilizumab in patients with active polyarticular-course juvenile idiopathic arthritis who have an inadequate response to, or were intolerant of methotrexate. In Part I of the study, all patients received intravenous (iv) infusions of tocilizumab (8 mg/kg for patients ≥ 30kg, 8 mg/kg or 10 mg/kg for patients < 30kg) every 4 weeks for 16 weeks. In Part II of the study, patients with an adequate response in Part I were randomized to receive either tocilizumab at the same dose as in Part I or placebo every 4 weeks for up to 24 weeks. In Part III of the study, patients received tocilizumab at the same dose as in Part I every 4 weeks for up to another 64 weeks. Standard of care therapy with or without non-steroidal anti-inflammatory drugs (NSAID), corticosteroids, or methotrexate was continued throughout the study.