Purpose: Patients with Stage IA Grade (G) III, Stage IB GII-III and Stage IC GI-II-III endometrial cancer who received postoperative adjuvant radiotherapy were evaluated in terms of local control, disease-free and overall survival rates and prognostic factors. Materials and Methods: Four hundred and three patients with Stage I endometrial cancer treated with radiotherapy from January 1990 to December 2003 at Ege University Faculty of Medicine Department of Radiation Oncology were reviewed retrospectively. According to our radiotherapy protocol patients with Stage IB G2 disease (149 patients) received only external radiotherapy and the remaining (254 patients) received both external radiotherapy and intracavitary brachytherapy. Results: Median age of the patients was 58 (range: 37-83). Nine patients (2.2%) had Stage IA, 196 (48.6%) had Stage IB and 198 (49.1%) had Stage IC disease. Histologic grade was 1 in 52 (12.9%) patients, 2 in 268 (66.5%) patients and 3 in 83 (20.6%) patients. Seventy-one (17.7%) patients had lymphovascular space invasion. Five-year locoregional relapse-free, distant-free, disease-free survival (DFS) and overall survival (OS) were 98.2%, 92.8%, 91.8% and 87.7%, respectively. In multivariate analysis, myometrial invasion and lymphovascular invasion were predictive factors for DFS and for OS prognostic factors were histologic type, myometrial invasion, and histologic grade. During radiotherapy 47.9% of the patients developed acute morbidity and 26.3% developed late morbidity, vaginal stenosis being the most frequent late morbidity. Conclusion: Postoperative adjuvant radiotherapy provides high locoregional control rates with acceptable toxicity in selected patients with Stage I endometrial carcinoma.