High-dose methotrexate (HD MTX) is usually administered as an inpatient to those with osteosarcoma. We prospectively tested the safety and feasibility of administering HD MTX in the ambulatory setting. In this single arm prospective observational study, eligible patients had previously completed 2 courses of HD MTX as an inpatient. On study, patients received MTX in hospital, discharged home and returned for daily assessment. Criteria to determine safety and feasibility included: (1) parent compliance with home instructions, (2) pump functioning/failure, and/or (3) admission for toxicity/noncompliance. Outpatient therapy was deemed feasible if <25% courses resulted in study event. Patient satisfaction was assessed. Six patients (median age, 13.5 y) with extremity osteosarcoma completed 35 courses of MTX. There were no study events-no hospitalizations or pump failures and all parents were compliant. The Data and Safety Committee concluded that with zero events in 35 courses, it was unlikely for outpatient MTX to be infeasible; study was thus terminated early. Participants reported value to stay out of hospital, permitted life to feel "more normal"; however, burden of daily commute to hospital was cited. The delivery of HD MTX is safe and feasible in patients with osteosarcoma.