It has been reported that camostat (Foy-305), a synthetic proteinase inhibitor, is excreted into the biliary-pancreatic juice in rats. To confirm whether camostat is excreted into bile or pancreatic juice, camostat (5 mg/kg/h) was given intravenously to dogs with pancreatic or biliary fistulae. Camostat and its active metabolite (Foy-251) in bile and pancreatic juice were measured by high-performance liquid chromatography (HPLC) and by their trypsin-inhibitory activity. Camostat did not alter the exocrine pancreatic secretion of fluid, bicarbonate, protein or trypsin stimulated by secretin (1 Crick-Harper-Raper unit/kg/h) and cerulein (50 ng/kg/h). Camostat and its active metabolite were detected in bile by HPLC and trypsin-inhibitory activity (the mean excretion rate was 1.3% of the intravenous dose of camostat), but they were not detectable in pancreatic juice. In conclusion, camostat and its active metabolite were excreted into bile but not into pancreatic juice.