A diagnostic ultrasound examination is a simple and reliable method of obtaining anatomical information for intracavitary irradiation of endometrial carcinoma of the uterus. Scanning before treatment to determine uterine size and shape assists in choosing the most appropriate applicator. Scanning after insertion of an afterloading applicator facilitates calculation of radiation doses at critical points within and on the surface of the uterus. Poor applicator position can also be detected. Diagnostic ultrasound examinations should be adopted as a routine procedure in establishing intracavitary irradiation programs for adenocarcinoma of the uterine fundus.