In this analysis, the results of brain irradiation of 39 patients with symptomatic brain metastases from oat cell carcinoma of the lung were compared with the published results of patients whose brains were irradiated prophylactically. The goals were: (1) to substantiate a clinical impression that patients with symptomatic brain metastases respond well to radiation and often experience no further neurologic deterioration until death; and (2) to compare the outcomes of symptomatic and prophylactic radiation of the brain for oat cell carcinoma of the lung. Of 39 patients with proven brain metastases who received cranial irradiation, 25 (64%) achieved complete palliation and remained free of neurologic symptoms, 4/4 (100%) achieved complete palliation; for moderate symptoms, 12/15 (80%); and for severe symptoms, 9/20 (45%). A summary of 12 reports from the literature shows that for patients with oat cell carcinoma of the lung receiving prophylactic cranial irradiation, the incidence of brain metastases is 28/525 (5%), while for patients receiving no prophylactic therapy it is 51/223 (23%). When the results of symptomatic and prophylactic cranial irradiation were compared, it was found that symptomatic irradiation controls central nervous system disease, as well as prophylactic therapy, while eliminating the need for brain irradiation in three-fourths of the patients.