A phase II study of cisplatin was performed in 13 previously untreated patients with unresectable biliary tract carcinoma. The drug was given intravenously at a dose of 80 mg/m2/day once every 4 weeks. Of 13 patients evaluated, 1 showed partial response lasting 3 months, while no patients showed complete response. Of 9 patients, whose serum level of carcinoembryonic antigen (CEA) was high (> or = 10 ng/ml) before treatment, 4 showed > or = 50% reduction in serum CEA level after treatment. The current study indicates that cisplatin does not have significant antitumor activity against biliary tract carcinoma.