Endoscopic papillary balloon dilation (EPBD) is considered to cause less trauma to the papilla than EST. However, it ha not been elucidated whether or not the preservation of papillary function is clinically meaningful. Aims: We compared papillary damage between post-EPBD and post-EST, and analyzed the incidence of later complications in each group. Methods:We evaluated the sphincter of Oddi function one year after treatment in each of 30 patients using a 4Fr. microtransducer catheter (Gaeltec Ltd.) via endoscopy.We also studied the incidence of pneumobilia and later complications in 171 post-EPBD patients and in 72 post-EST patients. Incidence of pneumobilia were detected by abdominal radiograph, ultrasonography, and computed tomography. Results: All manometric data, i.e., basal pressure, peak pressure and contraction frequency, was more reduced in post-EST patients than in post-EPBD patients, with a statistically significant difference. In 20 post-EST patients, the contraction wave had disappeared completely. The incidence of pneumobilia 1 year after the procedure was 8% (13/171) in post-EPBD patients and 47% (34/72) in post- EST patients. Recurrence of the stone was observed in 4% of post-EPBD patients and in 4% of post-EST patients in a period of one year, in 8% and in 6% for 2 years, in 8% and in 10% for 4 years, respectively. Cholangitis was observed in 0% of post-EPBD patients and in 3% (2/72) of post-EST patients. Gallbladder was preserved in 100 patients (58%) in the post- EPBD group and in 24 patients (33%) of the post-EST group, and cholecystitis was observed in 3% (3/100) and in 4% (1/24), respectively. Frequently recurrent cases (more than 3 times for 3 years) were observed in one post-EPBD patient and in 3 post-EST patients, and all of them presented pneumobilia. Conclusion: EPBD can preserve sphincter of Oddi function relative to the effects of EST. But it is still uncertain whether or not such preservations clinically meaningful.