Extensive evaluation of a small series of potential renal donors has revealed an alarming rate of previously unsuspected disease precluding acceptability for renal donation. Of 19 patients considered for donation at the Medical University of South Carolina, 15 were unsuitable for medical reasons (diabetes mellitus, multiple sclerosis, sickle cell trait, hypertension, polycystic kidneys, duodenal ulcer, pulmonary disease), psychologic reasons, or changes on renal arteriography consistent with nephrosclerosis. The importance of a thorough donor evaluation including total patient awareness of the risks involved for both himself and the recipient and extensive psychologic testing is stressed. Even with strict criteria for renal donation, this high rejection rate is surprising.