Partial hepatectomy has served as a valuable experimental tool with which to study liver regeneration and function. The presence of rather complete fissures between the hepatic lobes of laboratory animals has greatly facilitated resection and has provided a means of estimating the amount of tissue which has been removed. The techniques of partial excision in the rat2 and the dog1 are well standardized. Both methods are designed to resect about two-thirds of the liver and consist of ligating the base of the lobes to be removed with amputation of liver tissue distal to the ligature. Although this procedure is simple and rapid, it is associated with a high mortality where other surgical maneuvers are needed concomitantly (eg, partial hepatectomy and Eck fistula in dogs). This situation could be due to 1) excessive trauma of operation associated with retention of devitalized liver tissue, 2) production of a severe physiologic