Background: We evaluated the efficacy and safety of the aromatase inhibitor exemestane in patients with advanced, persistent or recurrent endometrial carcinoma. Methods: We performed an open-label one-arm, two-stage, phase II study of 25 mg of oral exemestane in 51 patients with advanced (FIGO stage III-IV) or relapsed endometrioid endometrial cancer. Patients were stratified into subsets of estrogen receptor (ER) positive and ER negative patients. Results: Recruitment to the ER negative group was stopped prematurely after 12 patients due to slow accrual. In the ER positive patients, we observed an overall response rate of 10%, and a lack of progression after 6 months in 35% of the patients. No responses were registered in the ER negative patients, and all had progressive disease within 6 months. For the total group of patients, the median progression free survival (PFS) was 3.1 months (95% CI: 2.0-4.1). In the ER positive patients the median PFS was 3.8 months (95% CI: 0.7-6.9) and in the ER negative patients it was 2.6 months (95% CI: 2.1-3-1). In the ER positive patients the median overall survival (OS) time was 13.3 months (95% CI: 7.7-18.9), in the ER negative patients the corresponding numbers were 6.1 months (95% CI: 4.1-8.2). Treatment with exemestane was well tolerated. Conclusion: Treatment of estrogen positive advanced or recurrent endometrial cancer with exemestane, an aromatase inhibitor, resulted in a response rate of 10% and lack of progression after 6 months in 35% of the patients.