To determine whether perfusion preservation affected the structure and survival of kidney transplants, we correlated clinical and histologic data in 77 kidneys biopsied one hour after ...transplantation. Twenty-one of 36 perfusion-preserved kidneys had a glomerular capillary lesion suggestive of intravascular coagulation. None of 41 kidneys preserved by hypothermia alone had this lesion. Presence of the lesion did not correlate with donor or recipient characteristics, warm or cold ischemia time, HLA match, percentage of preformed lymphocytotoxic antibody titers or perfusion characteristics. Of 21 transplants with the lesion, nine required nephrectomy by one month, and one-month serum creatinine was less than 2.0 mg per deciliter in only three of the remaining 12 transplants. We conclude that perfusion preservation may cause pathologic changes that may adversely affect kidney-transplant function. The causes of the pathologic process remain unclear.