Sphincterotomy has been advocated in the treatment of pancreatitis in order to minimize biliary reflux into the pancreas through a common outflow channel by diminishing resistance at the ampulla of Vater. This operation, which was first suggested by Archibald1,2 and later thoroughly investigated by Colp, Doubilet, and Mulholland,3-7 has had a varied degree of clinical acceptance. Experimental or clinical evidence of its efficacy in reducing the outflow resistance of the biliary tract over a prolonged period has been questionable. Judd and Mann found that sphincter section in normal dogs and cats reduced the yield pressure in the immediate postoperative period but the) made no measurements thereafter. Colp and Doubilet8 in 1936 measured the pressures in the common bile duct of seven dogs, two to six months after cholecystectomy and sphincterotomy, and reported them to be less than the mean value found preoperatively in other animals, but they