Patients with high grade, early stage endometrial carcinoma are reported to have worse survival and local control rates than those with low grade carcinomas. To define failure patterns further in patients with FIGO Stage I, grade 3 endometrial carcinomas, the patients from three institutions who received adjuvant or definitive radiation (RT) were analyzed. Of 119 patients meeting the criteria of Stage I, grade 3 endometrial carcinoma, 57 patients received preoperative radiation, 49 patients received postoperative radiation, and 10 patients received definitive radiation with 5-year actuarial survival rates of 64%, 73%, and 65%, respectively. Three additional patients received both preoperative and postoperative treatment. The overall local control rate was 88% with a median follow-up of 70 months. Of 36 patients who failed, 14 had a component of local failure, and 31 had a component of distant failure. Eighteen of 31 distant failures involved metastatic spread to the abdominal cavity. Recurrence patterns by method of treatment are documented. Patients with high grade tumors do have a propensity for distant metastasis. Clinical investigation into the value of systemic therapy is necessary.