We have investigated whether stenosis or insufficiency at the duodenal papilla results from the passage of a gallstone through the biliary tract. In three groups of patients after cholecystectomy we studied meal-stimulated pancreatic enzyme activity in T-drain bile from the common bile duct. Group A had gallbladder stones only; group B had gallbladder stones and bile duct stones; and group C had an episode of acute gallstone-induced pancreatitis, which was taken as direct evidence for gallstone migration into the duodenum. Reflux of pancreatic juice into the common bile duct was absent in group A, was occasionally found in group B, and was strikingly increased in group C. We conclude that passage of a gallstone through the biliary tract causes functional stenosis of the sphincter of Oddi and allows for a common channel between the pancreatic duct and the common bile duct. It does not cause sphincter insufficiency as previously assumed.