We report the results of a phase I study of intravenously administered cisplatin, 5-fluorouracil and high-dose folinic acid. This trial was designed to exploit potential biochemical interactions between these three agents. The maximum tolerated doses were cisplatin, 75 mg/m2, day 1; 5-fluorouracil, 375 mg/m2, days 1-5 and leucovorin 500 mg/m2, days 1-5. The dose-limiting toxic effect of this regimen was myelosuppression. Mild non-hematologic toxic effects were also observed and included nausea, vomiting, stomatitis, and diarrhea. Phase II trial of this regimen are underway, however randomized studies will eventually be necessary to establish whether cisplatin contributes clinically significant activity to this regimen.