A new endoscopic method, the peroral direct cholangioscopy (PDCS) is described. A prograde fiberscope of 8.8 mm diameter can be directly inserted, without using a second scope as a guide, into the biliary system after EPT (endoscopic papillotomy). The lumen of the common bile duct is observed entirely and exactly. The image is excellent. Also acessories may be inserted into the duct via the biopsy channel under direct control.