The aim of this study was to investigate the risk factors of postoperative anastomotic stricture after excision of choledochal cysts and hepaticojejunostomy. Among 65 patients who underwent surgery for choledochal cyst between March 1995 and June 2005, we selected 34 adult patients who were diagnosed as having choledochal cyst. We divided patients into two groups, depending on postoperative anastomotic stricture developed or not. Medical records and radiological findings of each patient were reviewed retrospectively. H&E stain and Masson-Trichrome stain of each specimen of the resected cyst were performed, and thickness of cyst wall, the grade of fibrosis, loss of smooth muscle layer, loss of mucosa, and infiltration of inflammatory cells were measured. Of the 34 patients, excision of choledochal cyst and hepaticojejunostomy were done in 33 patients, and 1 patient with chronic pancreatitis underwent pylorus-preserving pancreaticoduodenectomy. Anastomotic stricture and intrahepatic duct stones postoperatively developed in eight patients; one patient of 19 type I cyst and seven patients of 15 type IVa, developing significantly more in the type IVa choledochal cyst (P<0.05). The size of choledochal cyst in the stricture group was 7.0 cm, and that of the non-stricture group, 4.2 cm, showing significant difference between the two groups (P<0.05). The stricture group presented shorter duration of symptoms (27.63+/-61.72 days; ranged, 1 approximately 180 days) than the non-stricture group (483.33+/-916.41 days; ranged, 1 approximately 3,560 days), and it was statistically significant (P<0.05). Pathologically, significant difference was found between anastomotic stricture and infiltration of inflammatory cells (P<0.05). The results indicate that anastomotic stricture is influenced by the type IVa choledochal cyst, size of cyst, duration of symptoms, and the grade of infiltration of inflammatory cells. Therefore, closed careful follow-up is important in patients who underwent cyst excision with hepaticojejunostomy for type IVa choledochal cyst. If the anastomotic stricture develops, nonoperative management should be recommended, rather than operation, as much as possible.