Fourteen endometrioid carcinomas of the ovary with a prominent component of spindle-shaped epithelial cells are reported. Eleven were initially misdiagnosed as sexcord stromal tumors, malignant mesodermal mixed tumors, tumors of probable wolffian origin, or metastatic carcinomas. All of the tumors, however, had one or more features establishing them as endometrioid carcinomas, including (a) glands typical of endometrioid adenocarcinoma, (b) foci of squamous differentiation, and (c) an adenofibromatous component. Six cases were examined immunohistochemically, and the epithelial nature of the spindle cells was supported by immunostaining for keratin and epithelial membrane antigen. The patients ranged in age from 42 to 89 years (mean, 61). Four cases were stage I, five stage II, and three stage III. Follow-up information was available in seven cases. Five patients were free of disease at 8, 11, 32, 56, and 103 months, and two patients were alive with disease at 10 and 20 months. The age of the patients, clinical presentation, tumor stage, and gross appearance were similar to those of typical endometrioid carcinomas. It is important that this tumor be distinguished from other ovarian neoplasms with a spindle-cell component because of differences in treatment and prognosis.