A nationwide survey on Choledochal cyst was undertaken among 39 members of the Korean Association of Pediatric Surgeons. The members were required to complete a questionnaire and the case registration form for each patient during the five-year period of 1997 to 2001. Three hundred and forty eight patients were registered from 32 institutions. The average number of patients per surgeon was one to two every year. The male to female ratio was 1: 3.4. The age of patients on diagnosis was 49.0±44.4 months. The geographic distribution was 34.8% in Seoul and Kyoungki-do, 33.3% in Kyoungsang-do, 17.9% in Cholla-do, and 8.5% in Choongchung-do, in order of frequency. The three common clinical presentations were abdominal pain (63.8%), vomiting (35.3%), and jaundice (29.1%). Only seven patients (2%) presented with classic triad, and 25 patients were diagnosed by antenatal ultrasonographic examination. According to the Todani classification, 238 patients (71.3%) were type I, 3 (0.9%) type II, and 93 (27.8%) type IV. At the time of the operation, three important associated conditions were choledocholithiasis in 45 patients (15.1%), liver fibrosis (Grade 1-4) in 35, and previous operative procedure for biliary diseases in 10. Associated anomalies were observed in 13 patients (3.8%). Three hundred thirty nine (98.8%) of 343 lesions were treated by cyst excision and Roux-Y hepaticojejunostomy. One hundred seventy-six patients had an anomalous arrangement of the pancreatobiliary ductal system: APBD was not in 92 patients, biliary duct joined to the pancreatic duct in 51, and pancreatic duct joined to the biliary duct in 26. There were 8.5% early, and 7.7% late phase operative complications. The major complications were bleeding, anastomotic leakage, and acute pancreatitis. The combination of acute abdomen and choledochal cyst may suggest spontaneous rupture. Because of the development of late intrahepatic bile duct stones, long-term follow-up after cyst excision and hepaticojejunostomy is required. The optimal time of surgical intervention should also be considered in the situation of routine use of antenatal ultrasonographic examination. This is the first review of the choledochal cyst in Korea and provides baseline data for future comparisons.