The impact of obesity on graft survival after renal transplantation continues to be controversial. We have reviewed our experiences with living donor and cadaver transplantation in the current decade, focusing specifically on the impact of obesity on transplant outcome. Preoperative body mass index (BMI, kg/m2) was calculated for all adult renal transplant recipients between January 1990 and December 1995 and was used to classify patients as non-obese, moderately obese or morbidly obese. The effect of the degree of obesity on early and late outcomes after renal transplantation was examined. Three hundred and thirty-three recipients had pre-transplant BMI < 30 (normal or mild obesity), 68 BMI 30-40 (moderate obesity), and 7 BMI over 40 (morbid obesity). There was no correlation between obesity and other demographic factors. Wound infections and delayed graft function occurred more commonly in moderately and morbidly obese than in other cadaver donor recipients. Obese patients gained more weight after surgery and were given lower doses per kilogram of cyclosporine. There was, however, no significant correlation between obesity and graft survival for either cadaver or living donor transplants. Although obese patients have an increased risk of delayed graft function with cadaver donor transplantation, obesity has no discernible impact on either immunologic or overall graft survival with cadaver or living donor transplantation. The impact of moderate obesity on transplant outcome is modest and should not prevent these patients from receiving a transplant.