Performing sphincterotomy when either Billroth II gastrectomy or complicated periampullary diverticula are present may increase the risk of complications. In addition a sphincterotomy on the main pancreatic sphincter or the papilla of Santorini presents complicated problems. Stent-guided sphincterotomy has been utilized in 229 patients presenting to our institution from 1983 through 1992. They were performed in 67 patients who had undergone Billroth II gastrectomy, 23 with periampullary diverticula, 57 with pancreas divisum, and 82 with a history of recurrent pancreatitis. To prevent ductal injury or perforation, a stent is first inserted into the biliary or pancreatic duct to guide the sphincterotomy incision. The sphincterotomy is performed using electrocautery current delivered through a "needle knife" sphincterotome. Pancreatitis occurred in 19 patients (8.3%). It was mild in 17 and moderate in two patients. One patient experienced severe hemorrhage requiring surgery. No mortality or perforations occurred. The stent-guided needle knife sphincterotomy approach is an effective technique. It has a low complication rate even in these difficult anatomic conditions. It assures that the incision precisely follows the duct when performing pancreatic sphincterotomy.