This long-term, open-label extension study will evaluate the safety of RoActemra/Actemra (tocilizumab) in patients with polyarticular-course juvenile idiopathic arthritis who completed the WA19977 core study. Patients aged 9-18 years with at least JIA ACR30 clinical response to RoActemra/Actemra in the core study will be eligible to receive RoActemra/Actemra 8 mg/kg intravenously every 4 weeks. Anticipated time on study treatment is 104 weeks.

Inclusion Criteria:

• Patients 9 to 18 years of age who completed visit 33 (week 104) of WA19977 study with at least JIA ACR30 clinical response to RoActemra/Actemra relative to baseline in WA19977, with no AEs, SAEs or conditions that lead to unacceptable risk of continued treatment
• Females of child-bearing potential and males with female partners of child-bearing potential must agree to use effective contraception as defined by protocol

Exclusion Criteria:

• Patients with, according to investigator judgment, not satisfactory benefit from RoActemra/Actemra therapy within WA19977
• Treatment with any investigational agent since the last administration of study drug in the core study WA19977 or current participation in another clinical trial except WA19977
• Patient developed any other autoimmune rheumatic disease or overlap syndrome other than the permitted polyarticular-course JIA subsets: rheumatoid factor positive or negative JIA or extended oligoarticular JIA
• Patient is pregnant , lactating, or intending to become pregnant during the study and up to 12 weeks after the last administration of study drug
• Any significant concomitant disease or medical or surgical condition
• History of significant allergic or infusion reactions to prior biologic therapy
• Currently active primary or secondary immunodeficiency
• Current abuse of alcohol, drugs or chemical abuse
• Known and currently active acute, subacute, chronic infections or history of recurrent infection; patients suffering from ongoing active infections with Epstein Barr virus, herpes zoster or recurrent history of urinary tract infection can be included after the (acute) infection has been excluded or subsided
• Positive for latent tuberculosis (TB)
• Currently active asthma for which the patient has required the use of oral or parenteral corticosteroids for >/= 2 weeks within 6 months prior to entering the study
• Inadequate hepatic, renal or bone marrow function