Backgorund/Aims : Endoscopic choledochoduodenal fistulotomy(fistulotomy), using a needle-knife sphin-cterotome as an alternative to failed duct cannulation and subsequent endoscopic drainage in patients with ampullary cancer, can be performed in patients with a suprapapillary bulged or distorted papilla. The purpose of this prospective sutdy was to evaluate the safety and clinical usefulness of endoscopic fistulotomy in patients with ampullary cancer. Methods : Of the 29 patients with ampullary cancer requiring biliary drainage, 13 patients with a suprapapillary bulged papilla underwent fistulotomy either alone or followed by an upward extension of the fistulous orifice using a standard sphincterotome (fistulotomy group). Of the remaing 16 patients, transpapillary biliary stenting was successful in 13 patients (biliary stenting group). In both group, the rate of successful bile duct cannulation and effective biliary drainage were assessed and compared. Results : Bile duct cannulation was successful in 92.3% of the patients in the fistulotomy group and 81.3% of patients in the biliary stenting group, and the only complications were mild bleeding in 1 patient (7.7%) and cholangitis in 1 patient(6.3%). The success rate for initial biliary drainage with the fistulotomy or transpapillary stenting were 100% and 84.6%, respectively. Of the 12 patients in whom biliary drainage was used as the definite treatment, the symptom-free duration was 3.2 months in 6 patients of the fistulotomy group and 3.9 months in 6 patients in the biliary stenting group. Conclusions : Endoscopic fistulotomy is safe and effective for both preoperative and palliative biliary decompression in patients with ampullary cancer and it is suggested that the procedure can be applied primarily to increase the success rate of biliary access and subsequent biliary drainage especially in patients with a bulged papilla. (Korean J Gastrointest Endosc 2000;21:525-533)