Kidney transplantation is the best treatment for patients with end-stage renal disease and recipients of living kidney donors fare better than recipients of deceased donors. In view of the shortage of organ supply and the long waiting list, expansion of the living donor pool has been sought. Importantly, donor acceptance criteria must first and foremost be grounded in concerns for donor safety. Recent studies suggesting that live kidney donors may have higher rates of end-stage renal disease in the long term compared with otherwise similar healthy persons highlights the critical importance of pre-donation evaluation of renal function and structure, and careful application in donor selection criteria. The quality of organs from living donors may also affect recipient outcomes. Because donor kidney function, histology, and anatomy pertain to the quality of the donated organ, living donor characterization of the factors associated with these features is important to the donor as well as the recipient.