Objectives-Our objectives were (1) to review the rate of concurrent endometrial cancer in patients with a preoperative diagnosis of atypical endometrial hyperplasia (AEH); (2) to determine the proportion of patients with concurrent endometrial cancer who have high-risk disease; and (3) to re-evaluate our surgical management of AEH.Methods-We performed a retrospective chart review of all patients who had surgery on the basis of a preoperative diagnosis of atypical endometrial hyperplasia between January 2001 and December 2006. Demographic data, the method of preoperative diagnosis, postoperative grade of tumour, and other postoperative findings were recorded. When applicable, this included cancer stage, lymph node status, and presence of lymphovascular space invasion. In postoperative review, patients were considered to be high risk if they had disease beyond the uterus or a combination of other risk factors.Results-Of 70 patients, 25 (35.7%) were found to have concurrent endometrial cancer. This was higher than the commonly accepted rate of 25% (P = 0.03). Of the 25 patients upgraded, 4 (16%) had high-risk cancer on final pathologic evaluation.Conclusion-Simple hysterectomy in women with AEH may result in inadequate surgical management. Simple methods are required to identify patients with a preoperative diagnosis of AEH who may harbour significant cancers.