The efficacy of the long-lasting somatostatin analogue, octreotide, in the treatment of high-output pancreatic fistulas was investigated in this prospective, open study. Sixteen patients with post-operative pancreatic fistulas were treated with subcutaneous injections of octreotide 0.1 mg b.d. The output of the fistulas before the somatostatin therapy ranged between 190 and 570 ml/day. The therapy was begun on average 17 days following the appearance of the fistula (range 4 to 35 days). The decrease in volume one day after initiation of therapy ranged from 26% to 69%. By the third day of treatment the fistula volume decreased to 0-45% of the initial output. The treatment resulted in the closure of 14 of the 16 fistulas; the time to closure ranging from 3 to 15 days. The results suggest that octreotide is a useful adjuvant agent in the treatment of an external pancreatic fistula.