OBJECTIVE Some patients admitted for endoscopy present a gastrojejunostomy with a Billroth II anastomosis or Roux-en-Y reconstruction. The gastrointestinal reconstruction hampers endoscopic diagnosis and treatment of the biliary and pancreatic tract. The present paper describes a new procedure facilitating endoscopic retrograde cholangiopancreatography (ERCP) in patients who have undergone gastrojejunostomy. METHODS ERCP was attempted in 65 patients with gastrojejunostomy. A conventional side-viewing endoscope was advanced into the duodenal stump, and a modified catheter was pushed through the endoscope. The cutting wire of the modified catheter winds round the catheter at a pivotal point between the catheter's proximal and distal holes. This allows the catheter tip to be forced into an S-shape when the wire is pulled. Since the cutting wire can easily be adjusted to the papillary roof, safe and successful endoscopic sphincterotomy can be carried out. RESULTS We were able to advance the conventional side-viewing endoscope into the duodenal stump in 92% of the patients (n = 59) with Billroth II gastrojejunostomies, and in 33% of the patients (n = 6) with Roux-en-Y anastomoses. Whenever it was possible to reach the duodenal stump, cannulation and sphincterotomy of the papilla of Vater was successful. Ninety-six percent of the patients who underwent sphincterotomy (n = 54) immediately benefited from biliary decompression. One major complication occurred, with a patient suffering a retroperitoneal perforation during endoscopic sphincterotomy; the patient later died, despite three subsequent surgical operations. CONCLUSIONS In spite of previous gastrojejunostomy, most patients with Billroth II anastomoses (92%) and many patients with Roux-en-Y reconstructions (33%) can be treated endoscopically for biliary diseases. The use of a conventional side-viewing endoscope in conjunction with an S-shaped sphincterotome can be recommended. This allows safe and successful endoscopic treatment of all patients in whom endoscopic access to the papilla of Vater is possible.