A series of 790 patients with Stage I carcinoma of the corpus uteri, collected from 1940 to 1963, was divided into sets of prognostically distinct groups. The groups were arranged according to the patients age and histologic grade of their tumor. The uterine depth of the patients was used as well, where applicable. Within each group there was minimal variation in survival rates. The only major variable according to our data was therapy. Therefore, the relative merits of surgery and irradiation were readily comparable.Our study suggests that hysterectomy combined with irradiation (preoperative) appears to be the treatment of choice in Stage I cancer of the endometrium, except in the young patients with low grade tumors where surgery alone may suffice. In patients unable to withstand surgery, irradiation alone appears to be the treatment of choice.