Congenital dilatation of the common bile duct (choledochal cyst) is an uncommon disease. Although the etiology is unknown yet, various theories such as distal obstruction of the common bile duct, congenital weakness of the duct and anomalous union of the pancreaticobiliary duct have been offered to explain the occurrence of choledochal cyst. Thirty - six cases of choledochal cyst over 22 years were analyzed clinically and classified according to Todani's classification and Kimura's anomalous union of pancreaticobiliary duct type. Todani type I consisted with 22 cases which were subdivided into 19 cases of type Ia, 1 case of type Ib and 2 of type Ic. Type IVa consisted with 14 cases including one case of Caroli's disease. There were 25 type BP cases and 10 type PB cases and 1 normal pancreatobiliary junction. Serum alkaline phosphatase was increased significantly in almost all cases. Seven patients (19.4%) had associated congenital anomalies such as double gallbladder, left - sided gallbladder, common bile duct web, biliary atresia, accessory hepatic duct, heterotopic pancreas, cleft lip and 2 cases of intestinal malrotation. All patients underwent cyst excision and Roux - en - Y hepaticojejunostomy and cholecystectomy. There was one death due to methicillin resistant Staphylococcus aureus sepsis.