At the treatment of bile duct stones using EST, we sometimes experienced the difficult cases, even if the stones were small. For these cases, we tried endoscopic papillary balloon dilatation, and as a result knoches were made. And after the disappearance of the knoch, we could easily remove the stone. So we prospectively examined how often and at what cases, the knoches were made immediately after EST. As a result, knoches were present for 25% (13/52) of patients even after EST. Narrow distal segments of knoch-present patients were longer than that of knoch-absent patients, significantly. As a result, some function of sphincter was shown to be remained for a quarter of patients even after EST, and for these cases, the treatment of the stones may be difficult.