Thirty-eight women with advanced ovarian cancer resistant to alkylating-agent chemotherapy were treated with a combination of hexamethylmelamine and cisplatin. Hematologic toxicity was severe or life-threatening in seven of 13 patients treated with cisplatin at a dose of 100 mg/m2 but was acceptable in 25 patients treated at 75 mg/m2. Thirty-four percent of the combined group developed peripheral neuropathy and only 8% of those treated at 75 mg/m2 developed transient azotemia. Nine complete responses and 12 partial remissions were noted among 38 patients treated, with no obvious advantage for the higher dose of cisplatin. The median duration of remission was 8 months and the overall median survival was 9 months. The response rate of 55% is approximately twice that reported with either agent given alone in similar patient populations and is equal to or better than that reported for more complicated regimens containing these drugs together with other, less active drugs.