Increased activity against colorectal cancer by 5-fluorouracil (5-Fu) modulation with leucovorin (LV) and/or interferon (IFN) has been reported. In this study 22 patients with measurable advanced pancreatic cancer received 5-Fu 375 mg/m2 and LV 20 mg/m2 by i.v. bolus daily × 5 every 28 days plus IFN-α 3 million units/m2 s.c. There were three out of 21 (14%) responses lasting from 4 to 8 months. Sixteen patients (73%) had one or more episodes of grade 3 or greater toxicity (stomatitis, diarrhea or fatigue). While this combination has some activity against pancreatic cancer, its toxicity limits its potential as a palliative treatment.