The human bile duct has no intrinsic motility, but following cholecystectomy, flow through the bile duct is governed by the intraductal pressure generated by the liver, by the resistance to flow through the duct and sphincter at the terminal end of bile duct and by intraduodenal pressure. Pressure-flow experiments were performed upon 50 patients with biliary T-tube drainage following cholecystectomy and choledochostomy; nine patients had also undergone transduodenal sphincterotomy. Saline solution was introduced into the bile duct at controlled pressures, ranging from zero to 30 centimeters of water, while recordings were made of the flow rate of saline solution, intraduodenal pressure and respiratory movements. Although the flow rate of saline solution increased as its perfusion pressure was increased, three types of variation in flow were also recorded: rhythmic arrests of flow, occurring four to eight times per minute, believed to be due sphincteric contractions; nonrhythmic arrests of flow, lasting up to one minute, believed to be due to sphincteric contraction, and variations in flow associated with changes in intraduodenal pressure. The resistance to the flow of saline solution and the variations in flow rate were also similar in the patients who had undergone sphincterotomy. This study supports the view that sphincteric activity is present followingcholecystectomy, that the choledochal sphincter has rhythmic activity which differs from that of duodenal motility and that sphincter probably opens and closes continuously in a rhythmic manner during fasting periods in patients who have undergone cholecystectomy.