Disincentives for living kidney donation are common but are poorly understood. We studied 54 483 living donor kidney transplants in the United States between 2000 and 2009, limiting to those with valid zip code data to allow determination of median household income by linkage to the 2000 U.S. Census. We then determined the income and income difference of donors and recipients. The median household income in donors and recipients was $46 334 ±$17 350 and $46 439 ±$17 743, respectively. Donation-related expenses consume ≥ 1 month's income in 76% of donors. The mean ± standard deviation income difference between recipients and donors in transplants involving a wealthier recipient was $22 760 ± 14 792 and in 90% of transplants the difference was <$40 000 dollars. The findings suggest that the capacity for donors to absorb the financial consequences of donation, or of recipients to reimburse allowable expenses, is limited. There were few transplants with a large difference in recipient and donor income, suggesting that the scope and value of any payment between donors and recipients is likely to be small. We conclude that most donors and recipients have similar modest incomes, suggesting that the costs of donation are a significant burden in the majority of living donor transplants.