Background: Survival rate of ESFT in Japan was reportedly less than 50% in 1990s. The JESS started in order to improve this condition by conducting clinical trials for ESFT in Japan. Methods: This is a phase II, non-randomized trial to test safety and efficacy of multidisciplinary treatment for non-metastatic ESFT. Age under 30 is eligible. Chemotherapy regimens are alternating vincristine 1.5 mg/m² on day 1, doxorubicin 37.5 mg/m² on days 1 and 2, cyclophosphamide 1200 mg/m² on day 1 (VDC) and ifosfamide 1800 mg/m² on days 1 through 5 and etoposide 100 mg/m² on days 1 through 5 (IE) repeating every 21 days for 52 weeks. Local treatment includes surgical resection and/or radiation therapy, of which dosage varies from 0 to 55.8 Gy based on margin of the resection and pathological response. Primary endpoint is 3 year progression free survival (PFS). Statistical design was made to test whether the lower limit of 90% confidence interval (CI) of PFS will exceed the threshold of 60%. Planned sample size is 53 patients including 10% ineligible patients. Results: Fifty-three patients were registered from December 2004 to May 2008. Among the 53 patients, 7 patients were judged ineligible after the registration (metastatic disease 1, changed diagnoses 6). Forty six patients were considered as per protocol set and used for efficacy analyses. Three year PFS is 71.7% (90% CI: 0.59 – 0.81). Estimated 5 year PFS and OS are both 69.6%. Radiographic response rate (RR) in evaluable 38 patients is 71.1% and pathological RR in 25 is 52.0%. In safety data, hematological toxicities are significant such as grade 4 neutropenia observed in 98%. Although there is no previously unknown adverse event reported, there are three patients who experienced secondary malignancies (ALL 1, MDS 1, osteosarcoma 1). Conclusions: A multi-disciplinary treatment comprising standard multi-agent chemotherapy with vincristine, doxorubicin, cyclophosphamide, ifosfamide and etoposide improved outcome of Ewing sarcoma family of tumor in Japan although statistical confirmation of absolute efficacy was not successful.