Two patients with medically inoperable stage I endometrial carcinoma were treated with intracavitary implants alone using Simon capsules, tandems, and ovoids. In both cases, uterine thickness was measured during the implant procedure by realtime ultrasonography. Tumor doses in both patients were then calculated to the midmyometrium and to the serosal surface of the uterus. These estimates, rather than the usual milligram-hours or points A and B, were used to make treatment decisions.