OBJECTIVE We investigated the effects of splenectomy on the reduction of excessive portal hypertension immediately after adult living-related donor liver transplantation, paying particular attention to peritransplanted portal pressure in seven adult patients. METHODS We studied the relationship between portal hypertension and hyperbilirubinemia in small-for-size graft liver transplantation. RESULTS In the three cases, the portal pressures increased beyond 30 cmH2O after living-related donor liver transplantation, despite the right lobe graft, and these patients underwent splenectomy. After splenectomy, their portal pressures decreased below 25 cmH2O. The portal pressure underwent auxiliary orthotopic partial liver transplantation due to the hypercitrullinemia and did not change after surgery (9.5 to 11.5 cmH2O). Interestingly, the hyperbilirubinemia occurring after living-related donor liver transplantation were as the primary result of direct bilirubin except for the patient with citrullinemia. The posttransplanted portal pressures were controlled below 25 cmH2O in all patients, with their peak serum total bilirubin levels not exceeding 15 mg/dL, and the patients were discharged without major complications. Three patients underwent splenectomy, and did not suffer from serious infection. The reduction in excessive portal hypertension after living-related donor liver transplantation might prevent liver injury and post-transplant hyperbilirubinemia. CONCLUSIONS However, splenectomy remains a life-threatening factor. Therefore, transplant surgeons encountering living-related donor liver transplantation must continue to seek out additional solutions to problems with excessive portal hypertension.