We evaluated the effect of octreotide, a long-acting synthetic analogue of native somatostatin, on bowel frequency in 13 patients with AIDS-associated refractory diarrhoea. Cryptosporidium enteritis and cytomegalovirus colitis were the most common causes of diarrhoea. All patients received 100 μg t.i.d. octreotide subcutaneously for 1 week; those who did not improve were given 250 μg t.i.d. for a further 7 days. Bowel frequency returned to normal in 1 patient, who was affected with cryptosporidiosis, and decreased by more than 50% in 7 others, another patient improved on the higher dose. In 1 case, the beneficial effect disappeared after 10 days of treatment. No major adverse events due to the therapy were observed. We conclude that octreotide has a potential therapeutic use in severe AIDS-related refractory diarrhoea. How to identify patients who may respond remains unknown at present.