The relative risk of second tumors in patients with Ewing sarcoma is controversial, and little is known about their treatment and outcome. The purpose of the current study was to define the incidence and features of second tumors among 597 long-term survivors of nonmetastatic Ewing sarcoma treated with adjuvant and neoadjuvant chemotherapy, radiotherapy, and/or surgery. The authors found that the risk of secondary malignancy after adjuvant or neoadjuvant treatment of Ewing sarcoma is higher than that after other childhood or adolescent cancers only after radiotherapy. Based on this, postoperative radiotherapy should be avoided when surgery with adequate margins is feasible.