The effect of a long acting somatostatin analogue SMS 201-995 on stomal effluents in patients with severe short bowel syndrome was investigated in a double blind placebo controlled balance study. Six patients, five with Crohn's disease and one with radiation enteropathy were studied. Five patients had a jejunostomy and one an ileostomy. The patients had a normal food intake, but because of severe malabsorption had received home parenteral nutrition for several years. Faecal mass was reduced (p less than 0.005) and intestinal net sodium absorption was increased (p less than 0.005) by intravenous infusion of SMS 25 micrograms/h. Net absorption of potassium, calcium, magnesium phosphate, zinc, nitrogen and fat was not influenced. Subcutaneous injections of 50 micrograms SMS every 12 hours had a similar effect on net intestinal absorption of sodium and water. Four patients continued with a five to six months open follow up study when subcutaneous SMS in the same dose was administered by the patients at home. The effect on faecal sodium loss persisted, but in one patient faecal mass gradually increased and finally exceeded pretreatment values. SMS may decrease net absorption of water and sodium following reduced secretion of digestive juices rather than by increasing absorptive capacity. SMS may be useful as an antidiarrhoeal drug in patients with high output jejuno- or ileostomies, but in patients who need permanent parenteral nutrition the effect is too small to significantly alter management.