The remotely controlled afterloading apparatus, Toshiba RAL 303, was installed in Yonsei Cancer Center in 1979. The intracavitary irradiation method of high dose rate is very different from low dose rate such as radium 226. The irradiation of high dose rate is more effective for relative biological effects but is need precisely todosimetry and dose distribution in tissue. We described the properties of apparatus, protective room and itsadvantages and studied the arrangment of sources and dose distribution to be directly applied to Korean patients.The dose distribution varied considerably with arrangement of radiation sources, degree of vaginal extension,length and angulation of uterine cavity and mode of tumor growth to obtaine some indices for the optimumarrangement of radiation source and dose fractions, statistical evaluation was made on 82 patients who hadreceived the intracavitary radiotheraphy. Using the statistical evalution, radiobiological effects, computerprogram and simulating method, we established the therapy process and treatment planning of high dose rateintracavitary irradiation and provided the charts and diagram of the dose distribution according to arrangement ofsources.