We studied the results of radiotherapy in 65 patients with brain metastases of lung cancer. In the 34 patients whose treatment consisted of radiotherapy alone, the median survival time was 164 days and the mean survival time was 210 days. Remission was achieved in 29 (85%) of these patients, indicating that radiotherapy was effective. A minimum radiation dose of 30 Gy was necessary to decrease neurological symptoms, and 40 Gy or more was considered to be desirable. Survival after radiotherapy appeared to be dependent largely on factors other than brain metastases such as the effectiveness of management of the primary lesion, the presence or the extent of metastases to other organs, and the patient's general condition. Our study suggests that greater efforts must be made for early detection and early treatment to achieve prolongation of as well as qualitative improvements in the survival time.