SUMMARYThe new long‐acting somatostatin analogue octreotide (SMS 201–995) was investigated for its influence on segretatagogue‐stimulated human exocrine pancreatic secretion. Eighteen healthy volunteers participated in the study. During duodenal intubation with a background stimulation of either secretin 1 U.kg/h or secretin 1 U. kg/h + ceruletide, 120 ng.kg/h, octreotide was infused at doses of 5, 20 and 80μg/h in a placebo‐controlled randomized double‐blind crossover trial. Duodenal juice samples were collected in 10‐min intervals, and amylase, trypsin, chymotrypsin, and bicarbonate were measured in the individual fractions.During secretin stimulation, amylase was inhibited between 41 and 59%, trypsin between 28 and 72%, chymotrypsin between 55 and 70%, and bicarbonate between 0 and 31% with 5, 20 and 80μg/h octreotide. During secretin and ceruletide stimulation, amylase was significantly inhibited by 84%, 78%, 81%, trypsin by 76%, 55%, 52%, chymotrypsin by 77%, 55%, 60%, and bicarbonate by 25%, 11%, 19% with 5, 20, and 80μg/h octreotide, respectively (all decreasesP<0.05).The long‐acting somatostatin analogue octreotide was confirmed to be a potent inhibitor of stimulated human exocrine pancreatic secretion. The near maximal inhibitory potency of octreotide was achieved at a dose of only 5μg/h. This finding may be of value in the planning of therapeutic studie