Clinical Stage I carcinoma of the endometrium was evaluated in 222 patients. Twenty-five percent of patients were found to have pathologic findings thought to require postoperative external irradiation; of these, 20 of 57 (35%) had recurrence. During the 36- to 72-month follow-up period, only 14 of 165 (8.3%) treated only with operation (68 patients or 31%) or operation plus intracavitary radium (97 patients or 44%) manifested a recurrence. Furthermore, of all recurrences, 27 of the 34 (79%) were outside the pelvis. In these surgically staged cases, the absence of definable, demonstrable extrauterine disease was associated with a 7% recurrence rate versus a 43% recurrence rate if disease was found anywhere outside the uterus. Recurrence and death were correlated with other prognostic factors, which are outlined in this report.