431 patients were treated by radiotherpy for various malignant neoplasmsㅑㅜ different organs during the period of 1965 in the Radiation Therapy Division of the radiological research institute, Office of Atomic Energy. Among the 431 patients, 391 patients had completed a couse of treatment and 84 patients were unable to complete the therapy for various personal resons. We have reviewed the cases of 391 patients who have completed a course of Co-60 teletherapy during this period of time. Among the 391patients, 21 cases of Radium therapy and 2 cases of Strontium-90 treatment were included 83 percent of the patients were referred by teaching institutions and leading hospitals in Korea. There were 154 male patients and 237 female patients. The maximum cancer incidences were found in 50-59 years of age group for male patients and 40-49 years of age group for female patients. The commonest neoplasm in male was carcinoma of the larynx which represented 16.6% of all cancers in male treated. The next frequent neoplasm in male was carcinoma of the tongue, 10.4 %. Carcinoma of the head and neck was therefore commonest cancer accounting for 53.2 % of all neoplasms in male as compared with 13 % for cancer of the gastro-intestinal tract, and 11.7% for cancer of the lymphatic tissue system. Carcinoma of the cerrix was the predominant neoplasm in female accounting for 60.9 % as compared with 10.5 % for cancer of the breast. As this showed, gynecological organs were the site of approximately two thirds of all cancers in female. Most of the patients were treated by Co-60 teletherapy, and combination of Radium therapy with Co-60 teletherapy was utilized in 21 patients who belonged to the stage II group according to the clinical diagnosisof carcinoma of the cervix. Stontium-90 external treatment was applied to 2 patients who have superficial small lesion; one was hemangioma of tip of the tongue and other was pterygium of the eye.