In radiation therapy, a complete study of patients on the indication of radiotherapy, delicate considerationduring the radiotherapy, adequate after-care, the follow-up study and reconsideration are necessary. Theradiotherapy patients are quite different in treatment and care. It takes, time to evaluate. Sometimes themisjudgement of patients last several years. However, the great endurance and efforts are vital necessity for theradiotherapy evaluation and improvement of radiotherapy techniques. At the Radiological Research Institute, allthe radiotherapy patients from Nov.23, 1963 to Dec. 31, 1968 were observed, and among them, those who survivedthree years after radiotherapy were analyzed in order to report the difficulty in follow-up study and to helpformulate a better method of radiotherapy. All the follow-up study was done by questinaire form. We have sent 8,470 letters, and received 2,084 Positive answers (24.6%) and the retured and no-reply were 6,386(75.4%). As asample case, 121 patients, who reside in Chongro-ku Seoul. were selected for home-visiting by our staffs. 67 patients (48.6%) could he located easily where as 71 patients (51.4%) cold not be located. The results offollow-up correspondences were analyzed and categorized by the internation clacification of disease. Three-yearsurvivors and the surviving raate are listed.