Interest in nonimmunologic factors affecting longterm graft survival has focused on adequacy of nephron dosing. Body surface are (BSA) is a reliable surrogate for nephron mass. In a retrospective study of 378 primary recipients of paired kidneys from 189 cadaveric donors, we assessed the impact of matching donor and recipient BSA on outcome over 7 years. BSA of donors was 1.82 +/- 0.26 m2. Initially, paired recipients of kidneys from a single donor were divided into two groups. Group 1 included the recipient with the larger BSA of the pair (1.97 +/- 0.17 m2), while group 2 consisted of smaller BSA recipients (1.69 +/- 0.19 m2). Although early function was better in group 2 patients, graft survival at 1 year (77% vs. 79%) and 5 years (54% vs. 55%) was identical between groups, as were most recent serum creatinine levels (2.0 +/- 0.1 vs. 2.1 +/- 0.1 mg/dl). A second analysis divided patients with a functioning allograft at discharge from initial transplant hospitalization (n = 345) into three groups based solely on donor to recipient BSA ratio: the ratio of group A (n = 30) was < or = 0.8, that of group B (n = 255) was between 0.81 and 1.19, and that of group C (n = 51) was > or = 1.2. Graft survival and kidney function over 5 years did not differ among groups. In multivariate analysis of 17 variables, donor:recipient BSA, independent of other risk factors, did not affect risk allograft loss. These data indicate that including nephron mass as a criterion for cadaveric organ allocation is unlikely to improve long-term results in renal transplantation.