Carcinosarcomas (previously termed malignant mixed Müllerian tumors) are highly malignant but rare tumors of the ovary. Most patients have been treated according to a wide variety of protocols for soft tissue sarcoma or for epithelial ovarian carcinoma and as a result the optimal treatment for this neoplasm is unknown. We describe here 20 patients with this ovarian tumor (15 with heterologous sarcomatous elements and five with homologous sarcomatous elements) referred to our institute. Five patients were treated with surgery alone, two patients with chemotherapy alone and 13 patients with a combination of surgery and chemotherapy. A variety of chemotherapeutic regimens were used reflecting the 10-year time span it took to accrue these patients. Forty-five per cent of all patients died within 1 year of initial surgery and there was a median survival of 14 months. Two patients achieved a complete remission following treatment with 10 cycles of intravenous cyclophosphamide and are still alive at 103 and 106 months follow-up. We suggest that a chemotherapy regimen combining cyclophosphamide and a platinum analog may be useful for the management of patients with carcinosarcoma of the ovary requiring further therapy following surgery.