Abstract Analysis of 265 patients with adenocarcinoma of the endometrium treated at the Yale-New Haven Medical Center showed that older patients and those with an undifferentiated tumor had a less favorable prognosis. To permit comparison between the groups who received preoperative radiotherapy with one that received operation only, it was found necessary to adjust for differences in the incidences of the histologic grades among these two groups. This had a significant influence upon the interpretation of the survival rates in the patient with a histologically well-differentiated tumor. No relationship could be determined between survival and the size of the uterus in these patients nor between the radiation response (RR), sensitization response (SR), and the response of the tumor to radiotherapy. It is the feeling of the authors that histologic grade may prove the best subdivision for evaluation of results of tumor confined to the uterus.