Segmental liver volume determination by computed tomographic scan was carried out preoperatively in nine donors for living related liver transplantation. The calculated volume was compared with the graft size actually obtained by three types of donor hepatectomy. The volume of the left lateral segment (175 to 241 ml) and the left lobe (310 to 490 ml) varied markedly among the donors. The ratio of the left lobar to total liver volume also showed a wide range of values (23.2% to 35.9%). The value of the left lobar volume did not correlate positively with the donor's body weight, suggesting that graft size cannot be predicted only on the basis of the donor's body size. Segmental graft liver volume was estimated by use of computed tomographic scan, with acceptable accuracy on comparison with the graft volume actually obtained. In living related liver transplantation, the type of donor hepatectomy should be selected on the basis of the segmental liver volume of the donor in addition to the recipient's body size so that liver failure can be prevented in recipients and the donor's safety can be assured as far as possible. (HEPATOLOGY 1993;18:1115-1120).