Using a combined technique of hepatobiliary scintigraphy and gastrointestinal motility recordings, the changes in blood concentrations of cholecystokinin (CCK), secretin and pancreatic polypeptide (PP) were studied in relation to gastrointestinal motility and gallbladder dynamics in the interdigestive state in 7 healthy male volunteers. No changes in CCK concentration were found in relation to the migrating motor complex (MMC). In 3 subjects a slightly but insignificant elevated secretin level was seen during phase I of the MMC, otherwise no changes were observed. More pronounced fluctuations in PP appeared with significantly higher values during phase III compared to phase II. Values of concentrations of CCK, secretin and PP in periods with gallbladder filling were not significantly different from the values in periods of emptying.