In the living donor operation, accurate estimation of hepatic functional reserve is essential. Technetium-99m-galactosyl-human serum albumin (GSA) is a liver scintigraphy agent that binds to asialoglycoprotein receptors. We evaluated the preoperative assessment of the safety of an elective hepatectomy using GSA liver scintigraphy in 152 patients. GSA scintigraphy was performed after intravenous injection of GSA. The maximal removal rate of GSA (GSA-Rmax) was calculated using a radiopharmacokinetic model. We determined the areas for resection preoperatively depending on the operative procedures and calculated the local GSA-Rmax in the predicted residual liver (GSA-RL). A significant correlation was obtained between the GSA-Rmax and the 15-minute retention rate of indocyanine green. With sub- and monosegmentectomy, 2 patients had postoperative hepatic failure; in those 2 patients, the GSA-RL was 0.127 and 0.133, respectively, but these patients recovered well. Among those having di- and tri-segmentectomy, 5 patients experienced postoperative hepatic failure, in all subjects the GSA-RL was <0.15. Two patients died of postoperative liver failure 1 to 2 months after the operation. We concluded that GSA-RL is useful to select the procedure for hepatectomy in living donors and that GSA-RL should be >0.15 (mg/min/50 kg body weight) to avoid postoperative hepatic failure.