Clinicopathologic data are presented for 22 cases of malignant mixed mesodermal tumors of the ovary of both homologous and heterologous types. The results substantiate previous reports of low parity in the almost exclusively postmenopausal women with this tumor. Symptoms were the same as for ovarian malignancy in general. More than half the patients presented with stage III or IV disease, according to the International Federation of Gynecology and Obstetrics (FIGO) classification. Only four (19%) of 21 patients were alive at 18 months and had survived from three to more than 13 years. Their survival was associated strictly with stage I or II disease and with the purely homologous stromal pattern. Two tumors were contiguous with remnants of ovarian endometriosis. Differentiated malignant epithelium was most often of the serous/endome-trioid type, frequently with squamous zones, and was of the mucinous type in only one case. Whereas spindle cell stroma was present in many tumors of both stromal types, atypical cartilage was the predominant heterologous element.