Primary hyperoxaluria type 1 (PH1) is a rare inherited metabolic disorder in which deficiency of the liver enzyme AGT leads to renal failure and systemic oxalosis. Timely, combined cadaveric liver-kidney transplantation (LKT) is recommended for end-stage renal failure (ESRF) caused by PH1; however, the shortage of cadaveric organs has generated enthusiasm for living-related transplantation in years. Recently, successful sequential LKT from the same living donor has been reported in a child with PH1. We present a sister-to-brother simultaneous LKT in a pediatric patient who suffered from PH1 with ESRF. Twelve months after transplantation, his daily urine oxalate excretion was decreased from 160 mg to 19.5 mg with normal liver and renal allograft functions. In addition to the well-known advantages of living organ transplantation, simultaneous LKT may facilitate early postoperative hemodynamic stability and may induce immunotolerance and allow for low-dose immunosuppression. (Liver Transpl 2003;9:433-436.) P rimary hyperoxaluria type 1 (PH1) is a rare, inherited metabolic disorder caused by a deficiency of the liver-specific peroxisomal alanine-glyoxylate aminotransferase (AGT). It is characterized by increased synthesis and urinary excretion of oxalate that leads to renal failure attributable to urolithiasis, nephrocalcinosis, and, subsequently, to oxalate accumulation in various extra-renal tissues such as the skeleton and the cardiovascular system. Because the liver is the site of the metabolic defect, isolated kidney transplantation (KT) is not a reasonable therapeutic alternative because of a rapid diffuse oxalate deposition in the allograft. 1 Preemptive liver transplantation (LT) has been successfully performed in some children before serious renal damage occurred. 2 If end-stage renal failure (ESRF) has been reached, early simultaneous or sequential liver-KT (LKT) may avoid the deleterious consequences of systemic oxalosis. 3 Shortage of donor organs remains the critical factor limiting the use of organ transplantation. This shortage has generated enthusiasm for living-related transplantation, offering hope not only for children but also for adolescents and even adults. Partial LT alone or sequential LKT from living donors have been successfully performed for PH1. 4,5 To date, there have been no reports describing combined simultaneous LKT from the same living donor in the treatment of PH1 complicated with ESRF.