Octreotide inhibits intestinal motility and secretions of the gastro-intestinal tract and pancreas and mediators of diarrhoea and so is very useful in managing refractory diarrhoea. It is safe and effective in 75-80% of the 10-20% of cancer chemotherapy patients who develop severe diarrhoea, and is useful in the management of persistent diarrhoea associated with neuroendocrine tumours, particularly VIPoma and carcinoid tumours, congenital microvillus atrophy, some patients with the short bowel syndrome (giving them a reduced need for intravenous fluids), and AIDS-related diarrhoea that does not respond to antibiotics or conventional anti-diarrhoeal drugs. Some studies suggest a 50% effectiveness in graft-versus-host disease. Preliminary studies suggest that octreotide is also of value in persistent diarrhoea caused by neuromuscular disorders of the gut, particularly diabetes mellitus and systemic sclerosis, suggesting that it may have wider application in the future. Octreotide may prove useful as a tool for studying the pathogenesis of diarrhoea of diverse aetiologies, particularly those associated with disturbances of intestinal motility, such as irritable bowel syndrome.