The purpose of our study was to evaluate the association of race and ethnicity with outcomes in the living related donor (LRD) renal transplant population, using multivariable adjustment for potential confounding variables. We prospectively analyzed 14,617 patients from the UNOS Renal Transplant Registry who underwent LRD renal transplantations in the United States between January 1, 1988 and December 31, 1996 using the Cox proportional hazards model. This model adjusts for the effects of potential genetic, social, and demographic confounding variables that may be associated with race or ethnicity long-term graft survival. Blacks were 1.8 times as likely as whites (P < 0.01, RR = 1.77) to suffer graft failure during the 9-year study period, which decreased minimally to 1.7 (P < 0.01, RR = 1.65) after controlling for potential confounding variables. Neither genotypic nor phenotypic HLA matching improved outcomes in blacks. Black renal transplant recipients had lower graft survival even after adjustment for matching and rejection, suggesting that non-HLA or socioeconomic mechanisms may contribute to racial differences in transplantation outcomes.