Background-The Kidney Transplant Morbidity Index (KTMI) is a novel prognostic morbidity index to help determine the impact that pretransplant comorbid conditions have on transplant outcome. Objective-To use national data to validate the KTMI. Design-Retrospective analysis of the Organ Procurement and Transplant Network/United Network for Organ Sharing database. Setting and Participants-The study sample consisted of 100 261 adult patients who received a kidney transplant between 2000 and 2008. Main Outcome Measure-Kaplan-Meier survival curves were used to demonstrate 3-year graft and patient survival for each KTMI score. Cox proportional hazards regression models were created to determine hazards for 3-year graft failure and patient mortality for each KTMI score. Results-A sequential decrease in graft survival (0=91.2%, 1=88.2%, 2=85.4%, 3=81.7%, 4=77.8%, 5=74.0%, 6=69.8%, and >= 7 = 68.7) and patient survival (0=98.2%, 1=96.6%, 2=93.7%, 3=89.7%, 4=84.8%, 5=80.8%, 6=76.0%, and >= 7=74.7%) is seen as KTMI scores increase. The differences in graft and patient survival between KTMI scores are all significant (P<.001) except between 6 and Multivariate regression analysis reveals that KTMI is an independent predictor of higher graft failure and patient mortality rates and that risk increases as KTMI scores increase. Conclusion-The KTMI strongly predicts graft and patient survival by using pretransplant comorbid conditions; therefore, this easy-to-use tool can aid in determining outcome risk and transplant candidacy before listing, particularly in candidates with multiple comorbid conditions. (C) 2015 NATCO, The Otanization for Transplant Professionals