OBJECTIVE The objective of this retrospective study was to determine whether the difference between the donor's weight (wd) and the recipient's dry weight (wr) could influence the function of renal transplants. METHODS Between 1987 and 1994, 185 patients with a mean age of 43.3 years +/- 12 were transplanted with a locally harvested cadaver kidney, corresponding to 120 men (42.2 years +/- 1.4) and 65 women (45 years +/- 12.8). The weight variation between donors and recipients (wd - wr) was 0.06 for men and 0.22 for women. The serum creatinine of recipients at 1 year was 147 mumol +/- 41.7. We used analysis of variance for univariate statistical analysis and multiple linear regression for multivariate analysis. RESULTS On univariate analysis, the serum creatinine at 1 and 2 years was significantly higher (p < 0.02 and p < 0.035 respectively) when the donor's weight was 10% lower than the recipient's weight. Multivariate analysis, taking into account the donor's age and sex and the recipient's serum creatinine, confirmed the influence of the donor-recipient weight difference on serum creatinine at 2 years (p0.03), but also the role of the donor's age at 1 and 2 years (p < 0.0001 and p < 0.0004, respectively). CONCLUSIONS In our study, the donor-recipient weight difference was a factor influencing the recipient's serum creatinine at 2 years. The donor's age also influences the recipient's serum creatinine, 1 and 2 years after renal transplantation.