The extreme lack of renal grafts for transplantation stimulated us to analyze how strict the selection criteria of kidney donors must be. We investigated therefore if preexisting lesions in renal grafts influence initial and late renal function. 147 zero-hour biopsies of 101 donors (mean age 33, from 6-64 years) were examined. By ligh microscopy 38% of biopsies showed no, 44% showed nonspecific and 18% specific lesions. Nonspecific lesions comprised intimal fibrosis of small arteries in 44%, interstitial fibrosis in 8% and an arteriolar hyalinosis in 29%. Out of 102 immunohistologically examined biopsies 74.5% showed nonspecific IgM/C3 deposits in glomeruli and/or arterioles. An age dependent decrease of normal renal biopsies was found which was most evident in donors older than 40 years. Specific findings consisted of glomerulosclerosis (n = 4), glomerulonephritis (n = 11), intravascular coagulation (n = 10) and eclamptic kidney (n = 1). In case of nonspecific immunohistologic findings and in glomerulonephritis rebiopsies showed that antigen deposits usually disappeared within 4 months. Independent of morphologic findings 82% of transplant recipients had a good initial and late renal function. Since donor age, glomerulosclerosis, glomerulonephritis, intravascular coagulation or eclamptic changes seem not to compromise renal function after transplantation a more liberal choice of donors should be considered.