Purpose: The European Intergroup Cooperative Ewing's Sarcoma Study investigated whether cyclophosphamide has a similar efficacy as ifosfamide in standard-risk (SR) patients and whether the addition of etoposide improves survival in high-risk (HR) patients. Patients and Methods: SR patients (localized tumors, volume <100 mL) were randomly assigned to receive four courses of vincristine, dactinomycin, ifosfamide, and doxorubicin (VAIA) induction therapy followed by 10 courses of either VAIA or vincristine, dactinomycin, cyclophosphamide, and doxorubicin (VACA; cyclophosphamide replacing ifosfamide). HR patients (volume ≥100 mL or metastases) were randomly assigned to receive 14 courses of either VAIA or VAIA plus etoposide (EVAIA). Outcome measures were event-free survival (EFS; defined as the time to first recurrence, progression, second malignancy, or death) and overall survival (OS). Results: A total of 647 patients were randomly assigned: 79 SR patients were assigned to VAIA, 76 SR patients were assigned to VACA, 240 HR were assigned to VAIA, and 252 HR patients were assigned to EVAIA. The median follow-up was 8.5 years. In the SR group, the hazard ratios (VACA v VAIA) for EFS and OS were 0.91 (95% CI, 0.55 to 1.53) and 1.08 (95% CI, 0.58 to 2.03), respectively. There was a higher incidence of hematologic toxicities in the VACA arm. In the HR group, the EFS and OS hazard ratios (EVAIA v VAIA) indicated a 17% reduction in the risk of an event (95% CI, -35% to 5%; P = .12) and 15% reduction in dying (95% CI, -34% to 10%), respectively. The effect seemed greater among patients without metastases (hazard ratio = 0.79; P = .16) than among those with metastases (hazard ratio = 0.96; P = .84). Conclusion: Cyclophosphamide seemed to have a similar effect on EFS and OS as ifosfamide in SR patients but was associated with increased toxicity. In HR patients, the addition of etoposide seemed to be beneficial.