Advantages of direct peroral cholangioscopy (POC) using an ultraslim endoscope include use of conventional endoscopy equipment, operation by a single endoscopist, and superior image quality of the biliary tree with easy application of enhanced endoscopy and a large working channel. The major diagnostic indications of this system are an evaluation of biliary strictures, filling defects, or unclear find-ings on cholangiogram or other imaging studies. Therapeutic application using a direct POC system can be broadened by a larger work-ing channel. However, direct POC is difficult to apply in patients with a narrow diameter bile duct, far distal common bile duct lesion, or failed anchoring of the scope with accessories. An air embolism is a rare complication of direct POC but can be a fatal problem. Cholan-gitis can also occur during or after the procedure. Use of a CO2 system instead of room air during the POC procedure and administra-tion of antibiotics before and after the procedure are strongly recommended. Continuous development of specialized endoscopes and accessories is expected to facilitate the diagnostic and therapeutic roles of direct POC.