Peroral direct cholangioscopy (PDCS) is endoscopic method for diagnosis in the common bile duct (CBD) utilizing an ultra-slim upper endoscope. Clinical utility and problem of this method were investigated in ten patients who had stenosis or obstruction in the CBD with stones or a tumor. Scope shaft had to become the form of a U loop by counterclockwise rotation, to advance the scope in the direction of intrahepatic bile duct. As for one case, although the scope was formed alpha loop without U loop, direct observation of total CBC was possible. Large working channel of the endoscope could take adequate tissue sample by large biopsy forceps. Electrohydraulic lithotripsy and stone extraction with a basket could be accomplished easily and safely by direct visualization with a clear image. Pneumobilia was noted in all cases with insertion of PDCS. Although the abdominal pain and pyrexia with regard to PDCS did not occur, transient leukocytosis was noted.