This paper is a progress report on the role of radiation therapy (RT) in local tumor control and the decreased incidence of pulmonary metastasis in 251 patients entered in the Intergroup Ewing's Sarcoma Study. All were followed for more that 1 year, and their RT records were reviewed. Doses to the primary tumor in the range of 4,500--6,500 rad were administered over approximately 5 to 6 weeks in combination with 4 drugs, i.e., vincristine (VCR), dactinomycin (DAC), cyclophosphamide (CY), and adriamycin, or only the first 3. One group of patients received the 3 drugs and bilateral pulmonary irradiation (approximately 1,500 rad in 2 wk). Preliminary analysis showed a local primary tumor control of approximately 90%. Patients with lesions in the pelvis and humerus had local failure rates of 13% (7 of 54) and 21.4% (6 of 28), respectively. The treatment groups differed significantly in the incidence of pulmonary metastasis. Patients treated with the 4 drugs (regimen 1) had a 14% incidence, whereas 42% of those treated with only 3 drugs (regimen 2) developed pulmonary metastases. Of all patients treated with 3 drugs and pulmonary irradiation (regimen 3), 18% showed lung metastases. The study indicated that intensive chemotherapy and RT significantly improved the local control and survival of patients with localized Ewing's sarcoma. However, the high incidence of metastasis indicated the need for more effective systemic chemotherapy for further improvement of treatment results. More studies are needed so we can define the volume to be treated and the optimal dose of irradiation to determine a therapeutic strategy that will yield optimal survival and tumor control with the fewest sequelae.