Purpose : To evaluate the CT grading of complications developing after endoscopic sphincterotomy(EST), and their clinical course.Materials and Methods : We retrospectively evaluated CT in 19 patients in whom pancreatitis or duodenal perforation developed after EST in 594 patients. The CT grading of pancreatitis was classified as mild, moderate or severe, according to the extent of peripancreatic infiltration ; duodenal perforation was classified as mild, moderate or severe grade, according to the extent of fluid collection. We attempted to correlate CT grade with the average duration of hospitalizatioin after EST, treatment method and mortality.Results : Post-EST complications detected on CT were pancreatitis(ten patients, 1.7%) and duodenal perforation(nine patients, 1.5%). In those with pancreatitis, hospitalization after EST lasted an average of nine days in mild cases(n=2), 21 days in moderaten(n=1) and 41 days in severe(n=7). Nine of ten patients with pancreatitis were treated conservatively, while the other, whose grade was severe, underwent percutaneous drainage. Eight of these ten recovered ; the two died were severe grade patients, one having been treated conservatively and the by percutaneous drainage.In patients with duodenal perforation, hospitalization after EST lasted an average of 13 days in mild cases(n=2), 16 days in moderate(n=2) and 37 days in severe(n=5). Four of nine patients with duodenal perforation were treated conservatively, while the other five (severe, four ; moderate, one) underwent percutaneous drainage. One patient, graded as severe, expired, but the remaining eight rocovered. Percutaneous drainage was performed mostly in severe grade cases, and among patients thus graded, only three(3/594;0.5%) died.Conclusion : CT is considered useful for predicting the clinical course and prognosis of complications occurring after EST.