A randomized prospective comparison of treatment with cyclophosphamide and that with cyclophosphamide and cisplatinum, each in 21 patients with advanced ovarian cancer, has shown that the time to progression of tumor and the duration of survival were markedly improved in the patients receiving the combination chemotherapy. Cytoreductive surgery was performed in most of the patients in the study before the chemotherapy regimen was initiated. Second-look surgery was performed after a year of chemotherapy. The chemotherapy was administered on an outpatient basis, without excessive toxicity. At 2 years, 52.4% of the patients receiving combination therapy had no progression of tumor, whereas 9.5% had no progression of tumor inthe group of patients receiving a single alkylating agent. Survival at 2 years was 61.9% for the combination chemotherapy group and 19.0% for those treated with cyclophosphamide alone. The study demonstrates a striking superiority of combination chemotherapy over single-agent chemotherapy in patients with advanced ovarian cancer.