Obesity has generally been thought to increase the risk of operative mortality and postoperative complications in surgical patients. No data examining obesity as a factor in cadaveric renal transplantation were available. We therefore matched obese patients undergoing cadaveric renal transplantation with nonobese control patients and retrospectively analyzed mortality, morbidity, and graft survival in each group. Patients were matched for age, sex, diabetes mellitus, PRA, graft number, cardiovascular disease, date of transplantation, and posttransplant immunosuppression. There were significant differences found in mortality (11% in obese vs. 2% in nonobese patients, P less than or equal to 0.01), immediate graft function (38% in obese vs. 64% in nonobese patients, P less than or equal to 0.01), 1-year graft survival (66% in obese vs. 84% in nonobese patients, P less than or equal to 0.05), and postoperative complications. Wound complications (20% vs. 2%, P less than or equal to 0.01), intensive-care-unit admissions (10% vs. 2%, P less than or equal to 0.01), reintubations (16% vs. 2%, P less than or equal to 0.03), and new-onset diabetes (12% vs. 0%, P less than or equal to 0.02) were all significantly more common in the obese group. These results suggest that an attempt at significant weight reduction is indicated in obese patients prior to renal transplantation.