AbstractAs interest in the immunologic and energy substrate effect of partial hepatectomy has increased, a need for a reproducible model of hepatic resection has become necessary. The classic description for hepatectomy in small animals is the rat. In this report, we standardize the percentages of varying liver resection.C3H 8‐week‐old mice were subjected to 42% hepatectomy by removal of the right lobe and lateral aspect of the median lobe of the liver. Particular care was taken in ligation to avoid the gallbladder and to preserve the portal vein flow to the remaining lobes. The mortality rate for this procedure was 4%. Addition of the medial segment of the median lobe provided a 63% hepatectomy with 75% mortality. Using the operating microscope reduced this latter mortality to 17%.Important species differences exist between rat and mouse liver anatomy. The presence of the gallbladder in the mouse requires attention when employing mass ligature technique to avoid obstruction to the extrahepatic biliary tree. This can be safely and reproducibly accomplished if the hepatectomy is confined to the right lobe and lateral aspect of the median lobe. A more extensive hepatectomy in the mouse requires the operating microscope.