Living donor kidney transplantation offers many advantages to the recipient. Longer allograft survival, fewer postoperative complications and better renal function are just some of the benefits of receiving living donor kidneys compared to deceased donor organs. In contrast, the consequences to the donor in terms of renal function are less well defined. Moreover, it is not clear whether all donors share an equal risk to their renal function following donation. In this study, we calculated the estimated GFR (eGFR) by the MDRD formula in donors prior to and following renal donation. We compared the percentage decline in renal function amongst various ages and other demographic groups using individual patients as their own controls. Between 4/93 and 11/07, a total of 341 living donor transplants were performed in a single center. Of these, 103 donor charts (38 men, 65 women) were available for review. Donor characteristics were: 11 African American (AA), 94 white, age 40.3 9.6 years of age and pre-op eGFR 93.3 17.7 ml/min. All donors had normal blood pressures without medications, normal urinalysis and normal urinary protein levels. On average, donors experienced a -34.7% fall in eGFR to 59.8 10.9 ml/min determined 273 days post-transplantation. A greater decline in eGFR was noted in the AA group -41% compared to white patients -34% (p=0.03). The majority of the decline in the AA group was accounted by AA women in whom the fall in eGFR was -46% compared to AA men -31% and white women -34% (p=0.02). The percent decline in eGFR was not different amongst the various age groups. However, donors >50 years old had a post-donation eGFR of 55.1 ml/min vs. 60.9 ml/min in those < 50 years old (p=0.03) reflecting the lower eGFR pre-donation (older 84.7 vs. younger 95.2 ml/min, p=0.02). The percent decline in eGFR did not change with time after donation (0-1 month 37%, 1-12 months 34%, >1year 30%). These results suggest that renal function declines abruptly following kidney donation in all patients but remains stable or improves afterwards. AA women and older donors are at higher risk because they experience a greater immediate fall in eGFR and have a lower post-donation eGFR respectively. Clearly, a larger and prospective study is required to assess the potential renal functional decline in healthy living kidney donors.