Surface cooling and surface cooling plus 24 hours of pulsatile perfusion with oxygenated plasma were compared in a controlled study of methods of renal storage for transplantation. Using an immediate contralateral nephrectomy model, it was found that the three- and sixhour surface cooling ischemic interval could be extended at least 24 hours, and that some bettering of renal function occurred in perfusion-stored kidneys. This method is recommended for clinical transplantation.