Summary: A total of 161 uteri removed for cndometrial cancer were studied in order to characterize the histopathologic features of the endometrial surface epithelium. Of these, 116 had endometrioid endometrial adenocarcinoma, and 45 had other endometrial cancers. A total of 57 (49%) of the endometrioid endometrial adenocarcinomas showed the following surface epithelial changes: seven had a conspicuous microglandular pattern simulating cervical microglandular hyperplasia; 17 had syncytial aggregates of relatively bland-appearing eosinophilic cells, frequently with papillary or squamoid differentiation simulating papillary syncytial change or other endometrial epithelial metaplasias; and 33 had mixed patterns. The surface epithelial changes varied in extent from rare foci to extensive surface replacement and were largely confined to FIGO grade I and II tumors. Cytologic atypicality varied from mild to moderate and was consistently less than that of the underlying carcinoma. Similar changes were present in some of the prior curettings; in some scanty curettings an unequivocal diagnosis of carcinoma was not possible. Consequently, further clinical investigation is indicated if these changes are present in scanty curettings from postmenopausal women.