PURPOSE: The Ewing sarcoma family of tumors (ESFT) is a group of malignant tumors of soft tissue and bone sharing a chromosomal translocation affecting the EWS locus. The Intergroup INT-0091 demonstrated the superiority of a regimen of vincristine, cyclophosphamide, doxorubicin (VDC), and dactinomycin alternating with ifosfamide and etoposide (IE) over VDC for patients with nonmetastatic ESFT of bone. The goal of this study was to determine whether a dose-intensified regimen of VDC alternating with IE would further improve the outcome for patients with nonmetastatic ESFT of bone or soft tissue. METHODS: Patients with previously untreated, nonmetastatic ESFT of bone or soft tissue were eligible. They were randomly assigned to receive standard doses of VDC/IE over 48 weeks or a dose-intensified regimen of VDC/IE over 30 weeks. RESULTS: Four hundred seventy-eight patients met eligibility requirements: 231 patients received the standard regimen; 247 patients received the intensified regimen. The 5-year event-free survival (EFS) and overall survival rates for all eligible patients were 71.1% (95% CI, 67.7% to 75.0%) and 78.6% (95% CI, 74.6% to 82.1%), respectively. There was no significant difference (P = .57) in EFS between patients treated with the standard (5-year EFS, 72.1%; 95% CI, 65.8% to 77.5%) or intensified regimen (5-year EFS, 70.1%; 63.9% to 75%). Patients with soft tissue tumors accounted for 20% of the study population; there was no difference in outcome between patients with soft tissue and bone primary sites. CONCLUSION: Dose escalation of alkylating agents as tested in this trial did not improve the outcome for patients with nonmetastatic ESFT of bone or soft tissue.