Choledochoscopy is complementary to peroperative cholangiography in exploration of the main biliary way. Transcystic access is proposed in choledocholithiasis. The cystic duct, in fact, is frequently transitable owing to the dilatation produced by the migration of gallstones and because of the increasing miniaturisation of instruments. This examination of the MBW is less traumatic and risky than transcholedochotomic choledochoscopy.