A now 61-year old man with hypersecretion of vasoactive intestinal polypeptide (VIP) due to carcinoma of the tail of the pancreas was treated and followed for nine years. Combined administration of lomustin (2.5 mg/kg on day 1) and 5-fluorouracil (30 mg/kg on days 2-6) over eight courses at six-week intervals achieved clinical remission for 13 months. No clinical improvement was observed with streptozocin (500 mg/m2 on days 1-5) for two courses four weeks apart. Treatment had to be discontinued after the second course because of the onset of (rarely observed) neurotoxic side-effect of bilateral peroneal paresis. High doses of somatostatin (6.9 micrograms/kg hourly intravenously) immediately and markedly reduced stool quantity. But at a lower dose (3.4 micrograms/kg hourly i.v.) there was no noticeable effect. In the further course of the disease, massive attacks of diarrhoea at varying intervals were best controlled in intensity and duration by prednisolone (50-60 mg daily). Other drugs which have been recommended for such cases (indometacin, lithium, trifluoperazine, nicotinic acid and clonidine) had no worth-while effect. In future long-acting somatostatin analogues may provide better prospects for long-term treatment.