Recently, glyceryl trinitrate was shown to effectively dilate the smooth muscle of the sphincter of Oddi. This information was applied to endoscopic therapy of bile duct stones. In 21 patients a total of 32 common bile duct stones, 6-12 mm (means = 8.7 mm) in diameter, were removed through the intact sphincter after its medical dilation by administration of 1.2-3.6 mg glyceryl trinitrate. Thirty of 32 stones could be extracted without difficulty. The remaining two concrements had to be crushed by endoscopic mechanical lithotripsy before removal. No complications were observed during or after the procedure. Follow-up manometric examinations showed the papillary function to be well preserved. We therefore consider this new, safe, and easy method to be the treatment of choice for the removal of small- and medium-sized bile duct stones.