This Phase IV, multicenter, single-arm, open-label study will evaluate the efficacy and safety of tocilizumab in Chinese participants with sJIA with persistent activity and an inadequate response to non-steroidal anti-inflammatory drugs (NSAIDs) and steroid therapy.

Inclusion Criteria:

• Participants meeting International League of Associations for Rheumatology (ILAR) classification for sJIA
• Greater than (>) 6 months of documented persistent sJIA activity prior to screening
• Active disease
• hsCRP >4.3 milligrams per liter (mg/L) or 0.43 milligrams per deciliter (mg/dL)
• Participant who has recovered from any symptomatic serositis for at least 30 days prior to the screening visit, and requires a dose of CSs at baseline of </=30 mg/day or </=0.5 mg/kg/day, whichever is less
• Participants meeting one of the following: Participant who is not receiving MTX or discontinued MTX >/=4 weeks prior to baseline visit; participant who has been taking MTX >/=12 weeks immediately prior to the baseline visit and on a stable dose of </=20 mg/m^2 for >/=8 weeks prior to the baseline visit, together with either folic acid or folinic acid according to local standard of care
• Participant who was never treated with biologics or, if was previously treated with biologics, discontinued etanercept (or Yisaipu, Qiangke, or Anbainuo) >/=2 weeks, infliximab or adalimumab >/=8 weeks, anakinra >/=1 week, or abatacept >/=12 weeks prior to the baseline visit
• Participant who is not currently receiving oral CSs, or is taking oral CSs at a stable dose for >/=2 weeks prior to the baseline visit at </=30 mg/day or </=0.5 mg/kg/day, whichever is less
• Participant who is not taking NSAIDs, or taking </=1 type of NSAID at a stable dose for >/=2 weeks prior to the baseline visit and is less than or equal to the maximum recommended daily dose

Exclusion Criteria:

• Wheelchair bound or bedridden participant
• Any other autoimmune, rheumatic disease, or overlap syndrome other than sJIA
• Participant who is not fully recovered from recent surgery or <6 weeks since surgery at the time of screening visit; or planned surgery during the initial 12 weeks of the study
• Lack of peripheral venous access
• Any significant concurrent medical or surgical condition that would jeopardize the participant's safety or ability to complete the trial
• Evidence of serious uncontrolled concomitant diseases
• Asthma for which the participant has required the use of oral or parenteral CSs for >/=2 weeks within 6 months prior to the baseline visit
• Known human immunodeficiency (HIV) infection or other acquired forms of immune compromise or congenital conditions characterized by a compromised immune system
• Any active acute, subacute, chronic, or recurrent bacterial, mycobacterial, viral, or systemic fungal infection or opportunistic infection
• Any major episode of infection requiring hospitalization or treatment during screening, treatment with IV antibiotics completing within 4 weeks of the screening visit, or oral antibiotics completing within 2 weeks of the screening visit
• History of atypical tuberculosis (TB)
• Active TB requiring treatment within 2 years prior to screening visit
• Positive purified protein derivative (PPD) or T-spot test (interferon-gamma [IFN-γ]-based test) at screen
• Positive for latent TB
• History of reactivation or new onset of a systemic infection such as herpes zoster or Epstein-Barr virus (EBV) within 2 months of the screening visit
• Hepatitis B surface antigen (Ag)- or hepatitis C antibody (Ab)-positive
• History of macrophage activation syndrome (MAS) within 3 months prior to the screening visit
• Evidence of active malignant disease or diagnosed malignancies
• Uncontrolled diabetes mellitus
• Previous treatment with tocilizumab
• Intra-articular, intramuscular, IV, or long-acting CSs administration within 28 days prior to the baseline visit
• Treatment with non-biologic disease-modifying antirheumatic drugs (DMARDs; other than MTX) within 6 weeks prior to the baseline visit
• Treatment with leflunomide that was not followed by standardized cholestyramine washout and documented to be below the limit of detection prior to the baseline visit
• Treatment with cyclophosphamide, etoposide (VP16) and statins within 90 days prior to the baseline visit
• Treatment with growth hormone and androgens within 4 weeks prior to the baseline visit
• Administration of IV immunoglobulin within 28 days prior to the baseline visit
• Treatment with any cell-depleting therapies
• Stem cell transplant at any time
• Participant who has received live or attenuated vaccines within 4 weeks prior to the baseline visit, or intending to receive while on study drug or 3 months following the last dose of study drug