Endometrioid carcinoma is a malignant tumor which microscopically resembles endometrial adenocarcinoma, but arises from extrauterine sites, most commonly the ovary. Although its association with endometriosis has received considerable discussion, it appears that most of the malignant endometrioid tumors arise de novo. We present a case of endometrioid carcinoma which is outstanding for its primary site in the oviduct and for its histologic appearance, which incorporated a close interplay between both stromal and epithelial elements. The neoplasm was found incidentally, when the woman presented with postmenopausal bleeding due to adenomatous hyperplasia of the endometrium. The patient presented with a stage I, grade I tumor which did not invade the wall of the oviduct. Twelve years following a TAHBSO and postoperative radiation, the tumor recurred, requiring additional surgery and chemotherapy. The patient is currently disease free, 2 years from her recurrence. © 1991.