To determine if preoperative irradiation should be abandoned in favor of post-hysterectomy irradiation, 65 cases of stage I endometrial carcinoma were analyzed. When no residual tumor or no myometrial invasion was found in the irradiated uterus (38 cases), a 5-year cure rate of 97.3% was obtained. When residual tumor or myometrial invasion was found, there was a 5-year cure rate of 100% in grades 1 and 2 (7 cases) but only a 20% cure rate in grade 3 lesions (5 cases). On the basis of these data there appears to be no reason to abandon preoperative irradiation in stage 1 cases. More extensive irradiation and surgery should be considered, however, in grade 3 lesions invading the myometrium.