We studied relationship between an involvement of Oddi's sphincter in a choledochopancreatic junction and clinical appearances in 120 patients with anomalous arrangement of the pancreaticobiliary ductal system. The 120 composed of 83 with a sphincteric mechanism at the junction of the common bile and pancreatic duct and 37 without the sphincteric mechanism. We found that influences of sphincteric mechanism at the junction closely related to the length of the common duct between an orifice of the papilla of Vater and a junction of the common bile and pancreatic duct. And in all 83 with a sphincteric mechanism at the junction the length of the common duct showed less than 1.5 cm, and in all 37 without a sphincteric mechanism at the junction the common duct showed more than 1.5 cm in length. There was no correlation between a distribution of the sphincter muscle and clinical appearances, association with congenital choledochal cyst, cholelithiasis and bile duct cancer in the 120 patients.