The results are presented of thirty-seven patients with Ewing's sarcoma; ten were treated by a combination of operation, radiotherapy and cyclic chemotherapy, the remainder by radiotherapy and chemotherapy but without operation. The drugs, vincristine, cyclophosphamide and adriamycin were used in combination and were continued for two years. The follow-up ranged from twelve to sixty-two months. The mortality rate and the incidence of metastases were both markedly lower than in a comparable previous series treated by radiotherapy alone, or by operation plus radiotherapy, but all without chemotherapy. The percentage of local recurrences and of metastases was much higher in the twenty-seven patients who had radiotherapy and adjuvant chemotherapy, than in the ten in whom operation was also performed. It is suggested that on the basis of these results (and on theoretical grounds) treatment should consist of radiotherapy combined with chemotherapy plus, whenever feasible, operative excision of the primary tumour.