Anomalous junction of the pancreaticobiliary ductal system (AJPBDS) was found not only in 6 of 28 children with congenital dilatation of the bile duct, but in 3 of 57 children with congenital biliary atresia, in 2 of 17 children with infantile hepatitis and in one child with chronic pancreatitis during the past 17 yr at the Kagoshima University Hospital. A new technique of selective choledochopancreatography has been developed in which the mid-choledochus is clamped and dye is selectively injected into the distal choledochus to demonstrate the pathology of the bile duct. This technique has been successful even in small children when other cholangiographic techniques have failed to show AJPBDS. AJPBDS can be divided into two main types: (1) with biliary tract dilatation and (2) without biliary tract dilatation. The preferred treatment for type 1 is considered to be Roux-en-Y limb hepaticojejunostomy with primary excision of the choledochal cyst in order to prevent reflux of pancreatic juice flow into the choledochus, postoperative gall stone formation, or cancer from arising in the remaining choledochal cyst. Hepatic portocholecystostomy for biliary atresia with patency between gall bladder and papilla duodeni associated with AJPBDS can not be recommended since it may cause dilatation or obstruction of the bile duct postoperatively. Further studies concerning the etiology or therapy for AJPBDS are necessary.