A 72-year-old man with Crohn's disease for about 6 years was urgently hospitalized in hypovolaemic shock. On admission, serum creatinine concentration was 4.2 mg/dl, serum sodium 124 mmol/l, as a result of massive fluid and electrolyte loss via a loop ileostomy which had been placed 4 weeks previously because of a complicated perianal fistula. The basic aetiology of the diarrhoea probably lay in the previous resection of 30 cm of terminal ileum, other possible causes having been excluded. The ileostomy diarrhoea persisted despite the administration of loperamide, ranitidine, glucocorticoids, opium and pancreatic enzymes. Metronidazole, given in case the diarrhoea was due to a change in bacterial flora, also failed to achieve improvement. But when the somatostatin analogue octreotide was administered, the fluid loss via the ileostomy was quickly reduced so that both fluid and electrolyte infusions could be stopped. In subsequent months the initially required daily octreotide dosage of three times 100 micrograms could be reduced to once 50 micrograms subcutaneously. But it was not possible to stop this drug completely: it has now been continued and well tolerated for 2 years.