Specimens of the extrahepatic biliary trees and wedge liver biopsies were studied in 11 cases of biliary atresia. The hepatic arteries at the porta hepatis were examined with ultrasound in five of the 11 cases. The basic histopathological features were found to be epithelial damage and an inflammatory, sclerosing change of both the intrahepatic and the extrahepatic biliary trees, combined with an arteriopathy manifesting as hyperplasia and hypertrophy of the hepatic arteries in all cases. Based on the results of ultrasonography and histological examination, this arteriopathy was thought to affect the arteries from the trunk of the common hepatic artery to its peripheral branches supplying the entire biliary tree. To determine whether these morphologically abnormal hepatic arteries are related to the pathogenesis of biliary atresia in association with abnormal blood flow and pressure requires further investigation.