The effect on the liver of portal vein and/or bile duct branch ligation was examined in rabbits by measuring cellular kinetics using the bromodeoxyuridine labeling index. Twenty-four days after ligation of a portal vein and/or bile duct branch, similar degrees of compensatory regeneration were observed. However, there were significant differences in the pattern in which regeneration developed. Compensatory regeneration after ligation of a bile duct follows a different pattern than that after portal vein branch ligation.