Interferon alpha-2a (IFN-alpha) and folinic acid (FA) have been shown to modulate the cytotoxic effects of 5-fluorouracil (5-FU) in the treatment of cancer. A phase II study was initiated to evaluate the effect of a combination of 5-FU/FA/IFN-alpha in patients with advanced pancreatic cancer. Sixty previously untreated patients with advanced adenocarcinoma of the pancreas were treated with 500 mg m-2 FU via an intravenous bolus 1 h after the initiation of a 2 h infusion of 500 mg m-2 FA. Before starting the FA infusion, 6 million units (MU) of IFN-alpha was administered subcutaneously. The treatment was repeated once a week. Of 57 evaluable patients, eight (14%) had a partial response (PR), eight (14%) a minor response (MR) and 28 (49%) no change of disease (NC). Thirteen patients (23%) had progressive disease (PD). The median survival time was 10 months for all patients, 22 months for patients with partial remission and 5 months for patients with progressive disease. Many patients with tumour-related pain whose tumours were affected in terms of PR, MR, NC were free of pain during treatment with this regimen (22/36 patients). The common toxicities observed were fever (56%), nausea (37%) and diarrhoea (33%). These data suggest that biochemical modulation of 5-FU with FA and IFN-alpha has some positive effects in the treatment of pancreatic cancer of moderate toxicity.