To assess the relationship between the timing of radiotherapy and the risk of local failure in patients with endometrioid-type endometrial cancer who had undergone surgery and adjuvant external pelvic radiotherapy (with or without brachytherapy), but not chemotherapy. PATIENTS AND METHODS: One hundred and seventy seven patients were analyzed in this study. The median follow-up of the survivors was 72 months. RESULTS: Radiotherapy was delivered after a median time of 14.6 weeks from surgery and the median overall treatment time was 6.4 weeks. The tumor relapsed in 32 (18.1%) patients after a median time of 21 months. The local recurrence (vaginal or central pelvic) occurred in 11 patients. The local recurrence rate was associated with tumor grade (p=0.02), myometrial invasion (p=0.046), FIGO stage (p=0.003), pathological node status (p=0.037) and time interval from surgery to radiotherapy using 9 weeks as the cut-off value (p=0.046), but not with the overall treatment time. All the local relapses occurred in patients who received adjuvant irradiation after an interval from surgery >9 weeks. CONCLUSION: The time interval from surgery to radiotherapy might affect the local recurrence rate in patients not receiving chemotherapy. Every possible effort should be made to start radiotherapy within 9 weeks, when radiotherapy only is deemed necessary as adjuvant treatment.