To determine subcutaneous-tocilizumab (SC-TCZ) dosing regimens for systemic juvenile idiopathic arthritis (sJIA) and polyarticular JIA (pJIA).In two 52-week phase 1 b trials, SC-TCZ (162 mg/dose) was administered to sJIA patients every week or every 2 weeks (every 10 days before interim analysis) and to pJIA patients every 2 weeks or every 3 weeks with body weight ≥30 kg or 5th percentile of that achieved with IV-TCZ was achieved by 49 (96%) sJIA and 52 (100%) pJIA patients. In both populations, pharmacodynamic markers of disease were similar between body weight groups. Improvements in Juvenile Arthritis Disease Activity Score-71 were comparable between SC-TCZ and IV-TCZ. By week 52, 53% of sJIA patients and 31% of pJIA patients achieved clinical remission on treatment. Safety was consistent with that of IV-TCZ except for injection site reactions, reported by 41.2% and 28.8% of sJIA and pJIA patients, respectively. Infections were reported in 78.4% and 69.2% of patients, respectively. Two sJIA patients died; both deaths were considered related to TCZ.SC-TCZ provides exposure and risk/benefit profiles similar to those of IV-TCZ. Subcutaneous administration provides an alternative administration route that is more convenient for patients and caregivers and that has potential for in-home use.ClinicalTrials.gov, NCT01904292 and NCT01904279.