BACKGROUND Grafts from older donors or those in recipients with a greater body mass index (BMI) as compared with the donor may develop hyperfiltration syndrome that shortens renal graft survival. OBJECTIVE To assess whether the differences in weight and BMI between donor and recipient correlated with renal function, proteinuria, or graft survival among recipients of grafts from expanded criteria donors. METHODS We undertook a prospective, observational study in 180 recipients of grafts from expanded criteria donors performed between 1999 and 2006. All grafts had been biopsied previously for viability. The recipients underwent immunosuppression with basiliximab, late introduction of tacrolimus, mycophenolate mofetil and steroids. The study population was divided into three groups, depending on the tertile of the donor-to-recipient weight ratio (<1, n=64; 1-1.2, n=56; >1.2, n=60), and the donor-to-recipient BMI ratio (<0.97, n=59; 0.97-1.13, n=60; >1.13, n=60). The glomerular filtration rate was estimated from the modified diet in renal disease (MDRD) equation. RESULTS The mean age of the donors was 63.54 years and of the recipients, 58.38 years. The proportion of male-to-female donors was 52:48 and recipients 57.8:42.2 (P=NS). No significant differences in overall graft survival were observed between the tertiles. There was a negative correlation between the donor-to-recipient weight ratio and serum creatinine value at 1 (P<.001), 3 (P=.013), and 12 months (P=.005) after transplantation, and a positive correlation with the MDRD at 1 month (P<.001). No relation was noted between weight and proteinuria at 1 (P=.25), 3 (P=.51), or 12 months (P=.90). The results were similar after analyzing the ratio of the BMI to creatinine, MDRD or proteinuria, as well as in cases of a female donor to a male recipient. CONCLUSIONS Differences in weights between the donor and the recipient did not appear to affect graft survival or proteinuria among patients receiving grafts from expanded criteria donors, though it may be related to renal function during the early posttransplant stages.