The purpose of this work was to estimate the accuracy of frozen pathologic analysis, compared with final pathological diagnosis in patients with a preoperative diagnosis of endometrial complex atypical hyperplasia (CAH).We performed a retrospective review of frozen and final pathology in patients with a preoperative diagnosis of CAH from January 1987 through August 2004. Clinical and pathological information was obtained from patient charts.We identified 23 of 41 patients with diagnosis of CAH who had a frozen section. Nine of the frozen pathology results (39.1%) correlated with the final pathological diagnosis. In 14 of 23 of the cases (60.8%), the frozen and final pathology reports disagreed. Eight of 14 patients initially diagnosed with CAH by frozen section (57%) were diagnosed with endometrial adenocarcinoma on final pathology.Our data suggest that intraoperative frozen analysis of the endometrium is not a reliable indicator of final pathology in patients with a preoperative diagnosis of CAH.