The aim of this study is to analyze the impact of the recipient's disease severity on graft size requirements and outcome in adult-to-adult living donor liver transplantation. A limiting factor in adult-to-adult living donor liver transplantation has been adequacy of graft size. A minimal graft-recipient weight ratio (GRWR) of 0.8% to 1% has been suggested, without taking the recipient's disease into account. Forty adults underwent liver transplantation using left (n = 10; mean weight, 481 +/- 83 g) or right lobes (n = 30; mean weight, 845 +/- 182 g). We recorded graft survival, Child-Turcotte-Pugh score, and occurrence of small-for-size syndrome (poor bile production, prolonged postoperative prothrombin time, and cholestasis without ischemia markers). Small grafts were defined as GRWR of < or =0.85%. Large grafts were defined as GRWR greater than 0.85%. Six patients died within 6 months of transplantation (early patient survival rate, 85%); two patients died late of tumor recurrence. Among transplant recipients with normal liver function or Child's class A, there was no significant difference with the use of small (n = 6) or large (n = 9) grafts (graft survival rates, 83% v 88%, respectively; P =.65). Among patients with Child's class B or C, graft survival rates were 74% in recipients of large grafts (n = 19) and 33% in recipients of small grafts (n = 6; P =.023). Five of 6 patients with Child's class B or C who received small grafts developed small-for-size syndrome; 2 patients died (1 patient after retransplantation) and 3 patients survived (2 patients after retransplantation). Graft function and survival are influenced not only by graft size, but also by pretransplantation disease severity. GRWR as low as 0.6% can be used safely in patients without cirrhosis or in patients with Child's class A. Transplant recipients with Child's class B or C require a GRWR greater than 0.85% to avoid small-for-size syndrome and related complications.