Operative choledochoscopy: common bile duct exploration is incomplete without it. This paper reviews the reported experience of operative choledochoscopy. Development of choledochoscopes to the currently available rigid and flexible instruments is described. The collected results of both rigid and flexible choledochoscopy are reported. Retained stones occurred in 97 of 2712 stone-positive explorations with the rigid choledochoscope (3.6 per cent) and in 35 of 1726 stone-positive explorations with the flexible choledochoscope (2.0 per cent). Choledochoscopy should now be a mandatory part of common bile duct exploration. 