From November 1986 to April 1989, 16 patients with advanced measurable pancreatic carcinoma were involved in a pilot phase I-II study. 5-Fluorouracil was given every 3 weeks by 5-day continuous chronomodulated venous infusion (CMVI) with peak 5-FU delivery at 4 a.m. Intrapatient dose escalation started at 1200 mg/m2/day up to 1600 mg/m2/day in the absence of grade III (WHO) toxicity. Mucositis and diarrhoea were dose limiting in the 131 cycles given. Three partial responses (21%) and 5 stable diseases were seen in the 14 patients with measurable disease. Dose intensity after three or after six courses (1800 mg/m2/week) was significantly correlated with time to progression (Pearson r = 0.64; P < 0.004). These results, although modest, support a multicentre phase II trial with 5-FU CMVI.