Sixty-one patients with histologically proven ependymoma were irradiated between 1954 and 1976. Supra-and infratentorial tumors occurred more often in children and spinal cord--cauda equina tumors more often in adults. Local control was achieved in four of 20 supratentorial, 13 of 26 infratentorial, three of seven intramedullary spinal cord, and seven of eight cauda equina tumors. Improved local control of infratentorial tumors was noted for patients who received higher biologically effective doses of radiation but no dose-response for supratentorial, spinal cord or cauda equina tumors could be found. Five-year actuarial survival was 56% for all patients, 35% for supratentorial, 59% for infratentorial, 57% for spinal cord and 83% for cauda equina tumors. Spinal metastases were pathologically documented in 5 of 46 (11%) patients with ependymomas above the foramen magnum. They were clinically evident in two patients and most common in patients with infratentorial tumors whose spines had not been irradiated. One patient who was irradiated externally for cauda equina tumor developed radiation myelopathy 1-1/2 years later; three of eight patients who received intrathecal gold 198 developed myelopathy and/or cauda equina syndrome 3-1/2 to 17 years later.