A somatostatin analogue (SMS-201-995, hereinafter "octreotide") was s.c. administered to 5 healthy subjects under consecutive dripping of CCK-PZ (cholecystokinin-pancreozymin) and secretin (0.01 CHR U/kg/minutes), after inserting a Dreiling double tube into Treitz's ligament. Bile acid concentration, and bicarbonate and lipase excretions in duodenal juice were determined every 10 minutes up to 120 minutes and compared with controls. Moreover, octreotide (100 micrograms) was s.c. administered to 5 healthy subjects 30 minutes before meals for 7 days. Fecal fat and bile acid excretions before and after administration were determined. Bile acid concentration, and bicarbonate and lipase excretions in the octreotide group decreased to 1/3-1/4 that of controls. Bile acid concentration became 0 mM for 60 minutes. Fecal fat excretion increased; obvious steatorrhea occurred in 2 cases. Fecal bile acid excretion decreased to about 1/4. These results suggest that decreases in bile acid secretion should be considered, as well as pancreatic lipase and bicarbonate secretions, when fatty stool occurs after octreotide administration.