PURPOSE: This study was conducted to evaluate the clinical significance of choledochoscopy in biliary tract diseases. METHODS: We conducted a retrospective study of 291 patients who received choledochoscopy from October 1993 to December 1999. The indications of choledochoscopy were 259 cases of bile duct stones and 32 cases of benign and malignant biliary diseases: Klatskin tumor (n=10), intrahepatic cholangiocarcinoma (n=8), common bile duct cancer (n=6), hepatocellular carcinoma with bile duct invasion (n=2), and benign biliary stricture (n=6). The purpose of the choledochoscopy was 1) removal of bile duct stones, 2) differentiation between benign and malignant biliary diseases and 3) preoperative assessment of the extent and resectability of bile duct carcinoma. RESULTS: The success rate of complete stone removal was 80.1%, and the rate of recurrent biliary stones after a mean follow-up period of 24 months was 13.1%. The most common cause of a failure to remove the stones was biliary stricture. Differentiating between benign and malignant lesions, and the preoperative assessment of the extent and resectability of a bile duct carcinoma were accomplished by choledochoscopic observation followed by biopsy. The sensitivity in the diagnosis of malignant biliary diseases was 87%. The morbidity and mortality rates of choledochoscopy were 3.4% and 0%, respectively. With the exception of bile peritonitis due to tract rupture, any complications, such as cholangitis, bleeding, and pain, were conservatively managed. CONCLUSION: Our experience shows that choledochoscopyhas an important role in the diagnosis and therapy for benign and malignant biliary diseases and can be applied if indicated.