Nonoperative direct examination of the pancreaticobiliary system with an ultrathin fiberoptic endoscope was compared to endoscopic retrograde cholangiopancreatography (ERCP). Thirty-one patients were examined by both techniques. Direct examination of the biliary system was successful in 12 patients, seven of whom had had previous endoscopic sphincterotomy. In two patients it revealed stones missed on ERCP. In none of the patients was an examination of the pancreatic duct possible. ERCP visualized the biliary system in 28 patients and the pancreatic duct in 30 patients. In one patient the ERCP revealed a stone missed by the peroral choledochoscopy. Peroral choledochoscopy is complementary to ERCP and should be reserved for patients with probable pathology of the biliary tract and normal ERCP.