Recent advances in the molecular cloning of membrane transport systems that determine bile formation have facilitated studies of the molecular mechanisms of cholestatic liver disease. The present review summarizes what has been learned about the molecular alterations of these membrane transporters in hepatocytes and cholangiocytes in acquired cholestatic liver disorders. Much of this information has been obtained from the study of animal models of cholestasis and from more limited studies in clinical cholestatic liver diseases. Many of these responses may be interpreted as adaptations that serve to diminish cholestatic liver injury.