This study was undertaken to evaluate the outcome of pathologic stage III endometrial carcinoma treated with adjuvant radiation therapy (RT). A retrospective review was performed on 32 patients receiving adjuvant RT following abdominal hysterectomy for stage III endometrial carcinoma (19 IIIA, 2 IIIB, 11 IIIC) between 1980 and 1996. Papillary-serous and clear cell adenocarcinomas were excluded. Pathologic nodal sampling was performed on 25 patients (78%). All patients received postoperative external beam RT to the pelvis and 25 of 32 received an additional brachytherapy boost to the vaginal apex. Three patients with involved para-aortic nodes received extended field RT. Mean follow up was 70 mos. Twenty-four patients remain disease-free at mean follow-up of 68 mos. Distant recurrence (DR) occurred in 7 patients at mean of 38 mo. Two local failures were associated with DR. Six patients died of disease after recurrence despite salvage systemic therapy. One patient developed isolated local failure (vaginal apex) and remains disease-free 37 mo after surgical/chemotherapeutic salvage. 5 of 8 (45%) stage IIIC patients developed recurrence vs. only 2 of 19 (10%) stage IIIA cases. 2 of 3 patients treated with extended field RT for positive para-aortic nodal disease remain disease-free at 128 and 56 mo. Long-term survival can be achieved in stage III endometrial carcinoma. Few patients with either adnexal metastases or positive cytology alone develop recurrence. However, patients with stage IIIC disease fare poorly with local therapy alone.