CA-125 levels were determined in seven patients with a mixed mesodermal tumor of the ovary or endometrium. An elevated level was detected in five of six patients with metastatic or recurrent disease. Chemotherapy with cisplatin and Adriamycin (doxorubicin) resulted in a response in four patients, and the CA-125 level correlated well with the clinical status of the disease. Cisplatin/Adriamycin is an active combination in mixed mesodermal tumors and CA-125 appears to be a useful marker for following therapy.