Between 1969 and 1979, 22 patients with medulloblastoma were treated by the same surgical group and radiation therapy group. The patients were divided into two groups because of the clinical availability in December 1974 of the computed tomographic (CT) scanner and of the operating microscope used in the initial surgical procedure. There were 11 patients in each group. The percentage of patients with a relapse-free survival in the group treated between 1969 and 1974 (Group 1) was 38% at 4 years. The survival in the 11 patients treated between 1974 and 1979 (Group 2) was 84% at 4 years. This improvement is statistically significant (P ≤ 0.001). All patients received the same dose of radiation. Efforts to minimize the tumor burden by total surgical resection did not increase postoperative morbidity or mortality. These results are discussed, along with the relative impact of the CT scan, total resection at operation. and increased focus for radiation therapy on the improved outcome.