Eleven of 32 patients (34%) with advanced ovarian cancer previously treated with conventional therapies had partial or complete responses to 5-day courses of cis-diamminedichloroplatinum(II) (CDDP) (20 mg/m2/day) with nine showing objective response prior to initiation of the second course. Median duration of response was 6 months (range, 2-18 +). Response to CDDP was not correlated with age, pathologic subtype, tumor grade, or bulk disease but was correlated with response to prior treatment. Eight of 15 patients previously responsive to either single alkylating agents or cyclophosphamide plus doxorubicin (Adriamycin) responded to CDDP. In contrast, response to CDDP was observed in only three of 17 patients showing no response to this prior chemotherapy. The highest response rate to CDDP was seen in that subset of patients sensitive to cyclophosphamide and doxorubicin (seven of ten patients).