Thirteen patients with verified malignant mixed Müllerian tumor of the ovary treated in Denmark during the 7-year period 1981-87 were reviewed. Two patients had homologous and 11 patients had heterologous tumors. Four patients with early stage disease underwent radical surgery; 9 patients had stage III disease. Median survival for all 13 patients was 12 months. Six patients received platinum-containing cytotoxic therapy; 2 of these patients without measurable disease became long-term survivors (survival times 42+ and 92+ months, respectively) and 3 of the 4 remaining patients with evaluable disease obtained an objective remission.