To clarify the factors producing bile infarction and bile duct proliferation in obstructive jaundice, the incidence of the hepatic lesions and the serum levels of the bile constituents were examined in three rat models. (1) Ligation of the common bile duct induced bile infarction, bile duct proliferation, retention of bile in the liver, and elevation of the serum levels of total bilirubin and total bile acids. (2) The rats treated by choledochotomy had bile in the abdominal cavity, but there was no retention of bile in the liver. The degree of development of bile infarction was similar to that of the common bile duct ligation group, but bile duct proliferation was not found: the serum levels of total bilirubin and total bile acids were elevated. (3) In the rats subjected to partial bile duct ligation, bile infarction and bile duct proliferation were seen only in the lobes with ligation of the hepatic ducts: only slight or no elevation of the serum levels of total bilirubin and total bile acids was found. These data suggest that bile infarction is caused by the toxic action of bile constituents other than bilirubin and bile acids, absorbed into the blood from the obstructed biliary system, and that bile duct proliferation is due to mechanical factors following bile retention or direct actions of retained bile in the liver.