Eighty-six human kidneys have been preserved by cryoperfusion with an albumin-based perfusate for five to 50 hours prior to transplantation. Sixty-three of the kidneys were transplanted. The overall immediate function rate was 72% and was 100% (34/34) for kidneys with no warm ischemic damage transplanted into recipients without hypotension or prior sensitivity. The overall actuarial one-month kidney survival rate was 87%, the three-month survival was 73%, and the one-year survival rate was 65%. No kidney was discarded because of poor perfusion. Perfusion data, including flow, dastolic pressure, perfusion time, and lactate concentration were not predictive of immediate renal function. Light, electron, and immunofluorescence microscopic study of biopsy specimens showed no evidence of perfusion or immunologic damage to the kidneys. Perfusion of transplantable kidneys with albumin provides reliable preservation for up to 50 hours without producing either structural or immunologic damage to the organ.