Open liver biopsy specimens in sixty cases of biliary atresia were studied histopathologically, with particularly concerning the degeneration of intrahepaticbile duct (IHBD). Histopathological findings of the IHBD were classified into three groups, according to the severity of degenerative changes of bile duct: In group I (13 cases), degenerative changes were minimal and no bile plugs were identified. In group II (27 cases), degeneration was moderate and bile plugs were found in less than 10% of the total bile ducts. In group III (20 cases), severe degeneration and bile plugs were found in more than 10% of the total bile ducts. This classification of the degeneration of the IHBD was closely correlated to the age at operation and the degree of liver fibrosis. Severe bile cuct degeneration resulted poor bile flow after operation. Thus, the classifi-cation of the degenerative change of the IHBD is one of the most important factors, determin-ing the prognosis in biliary atresia patients.