A reliable method to preserve whole organs in vitro would have immediate application in clinical transplantation. Recently developed lymphocyte culture and lymphoagglutination histocompatibility tests are potentially capable of identifying suitable donor-recipient pairs in an outbred population.1 Unfortunately, the time required to complete these tests often prevents their use in cadaveric transplantation. A method of preserving organs for even a few days would permit the clinician to preselect the most compatible individual from a list of potential recipients awaiting cadaveric transplantation and would convert an emergent and hurried procedure into an elective operation. In addition, improved methods of organ preservation are needed to facilitate study of in vitro organ physiology. Hypothermia is a simple and readily reversible method for sharply reducing cellular metabolism and energy requirements. In the classic experiments of Calne, the use of hypothermia alone permitted reliable preservation of canine kidneys for only 12 hours.2,3 Canine kidney,