In this study, we analyzed the relative impact of donor and recipient variables on cadaveric renal allograft function and survival. The unique feature of the study population is that each pair of recipients received their allografts from a single donor. The study includes 378 adult patients. In 129 pairs both recipients were Caucasian, and in 60 pairs one recipient was Caucasian and the other was African-American. All transplants were done in one center, thus minimizing differences in preservation time and providing uniform posttransplant management. The initial analysis showed a relationship between the function of the allograft 6 months after transplantation (serum creatinine [SCr]6 mo) and donor variables (P = 0.0004, analysis of variance). Furthermore, it was calculated that 64% of the variability in the SCr 6mo among patients was due to donor factors and 36% was due to recipient factors. An elevated SCr 6 mo was significantly associated with older donors, male recipients, and patients with acute rejection episodes. Furthermore, other unidentified donor factors may have an impact on allograft function. Reflecting the importance of donor factors, there was a significant relationship between SCr 6mo in paired recipients (P < 0.0008 by Spearman). Analysis of racially dissimilar pairs showed that the SCr 6mo and graft survival 6 months after transplantation were not significantly different between Caucasians and African-Americans. However, beyond 6 months, graft survival was worse in African-Americans (P < 0.0001 by Cox). Compared with Caucasians, graft survival was significantly worse in African-Americans with poorly controlled blood pressure (mean arterial pressure > 105 mmHg) (P = 0.002, Cox), but not in those patients with mean arterial pressure < 105 mmHg. In conclusion, donor factors are major determinants of renal allograft function. However, those factors may not be easily identifiable or quantifiable. Donor factors do not contribute to racial differences in allograft survival. However, poorly controlled hypertension correlates with poor renal graft survival in African-Americans.