Background/Aims: Although initially endoscopic sphincterotomy(EST) has been performed for the removal of bile duct stone and drainage of the biliary tree, recently its spectrum has been widely extended for the management of various pancreaticobiliary diseases, Despite its relative safety, various complications - bleeding, acute pancreatitis, perforation, cholarigitis and sepsis - could be developed in about 5-10%. Even though the incidence of these complications has been well known, the studies focused on the risk factors of complication are lacking and ramain to be solved. The purpose of this study is to assess the various early complications of EST and elucidate the risk factors. Methods: The clinical records of 643 patients who performed EST between Jan. 1985 and Aug. 1995 were analysed. Analysis for tbe complications and risk factors were focused on 552 cases whose clinical records could be completely reviewed. Results: Arnong 643 patients, 368 were male and 280 were fernale and their mean age 59.3(25-88) years. Tjnderlying disease on where EST is performed were gallstone(373 cases), bile duct cancer(116 cases), gall bladder cancer(16 cases), benign bile duct stricture(20 cases), postoperative bile duct injury (8 cases), malignant bile duct obstruction(14 cases), pancreatic cancer(42 cases), pancreatic stone(12 cases), pancreatic leak(1 case), ampullary cancer(22 cases) and sphincter of Oddi dysfunction(14 cases). Overall success rate of EST was 94.9%(610/643 cases). Indications of EST were removal of bile duct stone(338 cases), drainage of bile duct(246 cases), peroral choledochoscopy(24 cases), peroral pancreatoscopy(3 cases), management of benign biliary stricture(8 cases), treatment of sphincter of Oddi dysfunction(14 cases), removal of pancreatic stone(9 cases), drainage of pancreatic duct(6 cases), obtaining cholangiogram(29 cases), transpapillary biopsy of pancreatic or biliary duct(23 cases). Early complications were developed in 7.6%(42 cases). Bleeding was the most common(16 cases). Others were acute pancreatitis(12 cases), sepsis(14 cases), and duodenal perforation(2 cases). Statistically significant risk factors for the developrnent of early complic,rtions were failure of EST, larger bile duct stone(> 2cm), failure of stone removal or biliary drainage(p=0.044, 0.009, 0.023, 0.047, respectively). The presence of juxtapapillary diverticulum and its location, common bile duct dilation, number of stone, type of papillotome were not influenced the development of complications. The significant risk factors for the bleeding were failure of EST, removal of stone and biliary drainage(p<0.0001, 0.004, 0.0004, respectively) and for the acute pancreatitis size of bile duct stone and ampullary buldging(p=0.037, 0.0001, respectively). Conclusions: These fin- dings suggest that the development of early complications of EST is mainly deJ>end on the failure of procedures undergone after EST, such as biliary drainage and stone remov;il rather than EST itse]f or other procedure not related conditions. Therefore the procedures after EST should be done carefully with full review to prevent the EST related early complications. (Korean J Gastroenterol 1997; 30:795-807)