As in the general population of the United States, obesity has become a significant problem in transplantation. Patient survival after deceased donor kidney transplantation is significantly lower among obese recipients (body mass index [BMI] > or = 30 kg/m2) than among non-obese recipients. Survival also appears to be decreased among obese liver transplant recipients. Based on these findings, some authors have argued against kidney or liver transplantation in the morbidly obese. However, the survival benefit for patients listed for and receiving either a kidney or liver transplant is not well understood. To determine if a significant survival benefit exists for obese patients after transplantation versus those on the waiting list, we studied a retrospective cohort of patients identified in the Scientific Registry of Transplant Recipients database. Adjusted, time-dependent Cox regression models were used to evaluate the relative risk (RR) of death after transplantation compared with waiting list mortality for either kidney or liver transplantation. These results demonstrate that kidney transplantation offers a significant survival benefit and is the preferred therapy for most obese dialysis patients. Although liver transplant recipients with a BMI > or = 35 kg/m2 had an increased RR for mortality compared with other recipients with a lower BMI, all groups, regardless of BMI, demonstrated a significant transplant benefit. These data suggest obesity should not be a contraindication for transplantation.