Endoscopic retrograde cholangiopancreatography was performed before laparoscopic cholecystectomy in 312 patients, with successful results in 287 patients (92.0%). Common bile duct stones were diagnosed in 26 of the 287 patients (9.1%). In eight of these patients, the diagnosis had not been suspected from the clinical or laboratory data or results of ultrasonography. Endoscopic sphincterotomy with stone removal was successful in all 23 patients who underwent this procedure. Anatomical variations were detected in 7 patients (2.4%), including origin of the cystic duct from the right hepatic duct and the accessory bile duct, and anomalous arrangement of the pancreaticobiliary ducts and choledochocele. Pancreaticobiliary malignancies were also diagnosed in 3 patients. The morbidity rate with diagnostic ERCP was only 0.7%. Preoperative ERCP proved highly useful and sale for determining biliary anatomy, and for detecting unsuspected stones or malignancies.