The influence of bile on the release of cholecys-tokinin (CCK) and, thereby, on the regulation of exocrine pancreatic function and growth is unsettled. The aim of this study was to elucidate the effect of long-term diversion of bile from the upper small intestine on CCK release and on the pancreas, liver, and gastrointestinal tract. A surgical biliodigestive shunt was performed in rats, diverting the bile flow directly to the middle of the small intestine. The animals were killed after 4 or 12 weeks. Plasma CCK and trophic effects on the pancreas, liver, and gastrointestinal tract were determined, as were the trypsin and chymotrypsin contents in the intestine. The CCK concentration in plasma increased 10-fold at both time points studied. The pancreas doubled its weight from 4 weeks onward. Also, pancreatic protein, DNA, and amylase contents were increased throughout the study. The liver and gastrointestinal tract were unaffected. Intraluminal bile plays a role in the feedback regulation of CCK release and is involved in this way in the control of pancreatic growth but has no similar effects on the liver or gastrointestinal tract.