The logic of cancer histopathology demands that the presence of tubal epithelium in the endometrium be followed in some cases by the corresponding carcinoma. With tubal epithelium, this carcinoma is the homologue of the serous carcinomas of the ovary or the usually encountered carcinoma of the oviduct. A series of 8 of these cases was studied. Many of the features were similar to those of ordinary endometrial carcinoma but the prognosis was strikingly worse; many of the patients died of widespread metastases, with no or only minimal myometrial invasion.