BACKGROUND The combination of 5-fluorouracil (5-FU) and cisplatin has shown great activity in many different types of tumour with an in vitro synergistic effect between 5-FU and cisplatin. A phase II study of 5-FU plus cisplatin was performed in 25 previously untreated patients with inoperable locally advanced or metastatic biliary tract carcinoma. METHODS Twenty-five patients, 10 of them men and 15 women with a median age of 58, were entered into the study. The chemotherapy regimen consisted of 5-FU: 1 g/m2/day in continuous intravenous (i.v.) infusion for five consecutive days, and cisplatin: 100 mg/m2/day on day 2 in a one-hour infusion with standard hyperhydration. Twenty-two patients had metastatic tumours and three had locally advanced disease. RESULTS Of the 25 patients entered into the study, 24 were evaluable for response and 25 for toxicity. Nausea and vomiting was the main toxic side effect in 19 patients. Severe, WHO grade 3-4 thrombocytopenia or neutropenia were observed in three and seven patients, respectively. There were no toxic deaths. Of 25 patients, six had partial remissions (overall response 24%, 95% confidence interval 7%-41%). For three patients, tumour reduction permitted local radiotherapy and one of these patients with initially advanced disease is still alive six years after the beginning of treatment. CONCLUSIONS This study, one of the largest phase II trials performed in this disease, shows interesting activity of the combination of 5-FU and cisplatin in advanced biliary tract carcinoma.