Somatostatin and octreotide both enhance closure of gastrointestinal fistulas. The present trial was undertaken to test whether early combined treatment with parenteral nutrition and octreotide 100 μg every 8 h by subcutaneous injection had a beneficial effect compared with parenteral nutrition plus placebo. Thirty‐one patients with postoperative gastrointestinal or pancreatic fistula were randomly assigned to receive parenteral nutrition plus octreotide (14 patients) or placebo (17) within 8 days of fistula onset. The percentage reduction in output and rate of spontaneous closure within 20 days were analysed. Mean(s.d.) reduction in output was similar after octreotide and placebo at 24 h (66(43) versus 68(47) per cent, P = 0.9), 48 h (60(46) versus 57(43) per cent, P = 0.8) and 72 h (62(50) versus 66(49) per cent, P = 0.9) after starting the combined treatment. Closure within 20 days was observed in eight of 14 fistulas in patients given octreotide and in six of 17 in those receiving placebo (P = 0.4). Administration of octreotide, within 8 days of fistula onset, associated with parenteral nutrition does not significantly increase the spontaneous fistula closure rate compared with parenteral nutrition plus placebo. Copyright © 1995 British Journal of Surgery Society Ltd.