Background: Little is known about the yield and accuracy of endoscopic examination with the duodenoscope after ERCP, and there appears to be no uniform standard of practice for endoscopic examination in this setting. Methods: Over a 1-year period, all patients undergoing ERCP also underwent endoscopic examination of the duodenum, stomach, and esophagus with the dyodenoscope upon completion of ERCP. Patients were then placed in the left lateral decubitus position and upper endoscopy was performed with a standard forward-viewing endoscope. The same investigator performed both endoscopic examinations. Patients were queried about prior ulcer disease, upper GI symptoms, and use of antisecretory medication as well as nonsteroidal anti-inflammatory drugs. Results: During the 12-month study, 368 patients (mean age 53 years) underwent 474 procedures. The most frequent indication for ERCP was suspected choledocholithiasis (24%). Endoscopic examination was normal in 42% of patients, and the most frequent endoscopic finding was hiatal hernia (132 patients, 36%). The lesions most frequently missed with the duodenoscope were trauma at the upper esophageal sphincter (12 patients) and small benign gastric polyps (3 patients). Examination with the duodenoscope was superior to the forward-viewing endoscope for identification of Schatzki's ring. No carcinoma, gastric varices, or severe esophagitis were missed with the duodenoscope. Conclusions: Given the frequency of endoscopic lesions, a yield of positive findings similar to that obtained with the forward-viewing endoscope, and the ease of performing endoscopy with the duodenoscope, endoscopic examination of the esophagus, stomach, and duodenum with the duodenoscope should become standard practice after ERCP. Copyright © 2002 by the American Society for Gastrointestinal Endoscopy.