431 patients were treated by radiotherapy for various malignant neoplasms in different organs during theperiod of 1965 in the Radiation Therapy Division of the Radiological Reserch Institute, Office of Atomic Energy.Among the 431 patients, 391 patients(82.3%) had completed a course of treatment and 84 patients(17.7%) were unableto complete the therapy for various personal reasons. We have reviewed the cases of 391 patients who havecompleted a course of Co-60 teletherapy during this period of time. Among the 391 patients, 21 cases of Radiumtherapy and 2 cases of Strontium-90 treatment were included.. 83 percent of the patients were referred by teachinginstitutions and leading hospitals in Korea. There were 154 male patients and 237 female patients. The maximumcancer incidences were found in 50-59 years of age group for male patients and 40-49 years of age group for femalepatients. The commonest neoplasm in male was carcinoma of the larynx which represented 16.6 percent (25 patients)of all cancers in male treated. The next frequent neoplasm in male was carcinoma of the tongue, 10.4 percent (16 patients) Carcinoma of the head and neck was therefore commonest cancer accounting for 53.2 percent of allneoplasms in male as compared with 13 percent for cancer of the gastro-intestinal tract and 11.7 percent forcancer of the lymphatic tissue system. Carcinoma of the cerrix was the predominant neoplasm in female accountingfor 60.9 percent (144 patients) as compared with 10.5 percent (25 patients) for cancer of the breast. As thisshowed, gynecological organs were the site of approximately two thirds of all cancers in female. Most of thepatients were treated by Co-60 teletherapy, and combination of Radium therapy with Co-60 teletherapy was utilizedin 21 patients who belonged to the stage II group according to the clinical diagnosis of carcinoma of the cervix.Strontium-90 external treatment was applied to 2 patients who have superficial small lesion; one was hemangioma oftip of the tongue and other was pterygium of the eye.