A case is presented in which the diagnosis of acute myelomonocytic leukemia was made 16 months after the start of irradiation and chemotherapy for Ewing's sarcoma. The association of these two diseases is rare. The etiologic role of therapy in the development of leukemia is speculative in this case. However, there is need for surveillance for secondary neoplasms of all types so that the benefits of therapy may be properly weighed against the risks.