Experimental studies on viability of the kidney preserved under hyperbaric and hypothermic condition were performed on dogs. The left kidney was removed and perfused with refrigerated (4℃.)low molecular weight dextran in electrolytic solution containing heparin. Immediately after perfusion, the kidney was immersed in a same solution as used for perfusion and stored in a hyperbaric chamber for 6, 12 and 24 hours, respectively under 3 atmospheres of oxygen pressure and 4℃. Following the storage, the kidney was reimplanted in the left iliac fossa of the original donor. The contralateral kidney was removed 3 weeks after the renal autotransplantation. Following results were obtained. 1) Perfusion of the kidney with low molecular weight dextran in electrolytic solution resulted in no significant increas of the kidney weight and in no development of interstitial edema. 2) There was no correlation between the histologic appearance of the preserved kidney and its viability. 3) After the contralateral nephrectomy all two kidneys preserved for 6 hours and two out of three kidneys preserved for 12 hours were able to sustain life but all 9 kidneys preserved for 24 hours were unable. 4) The precise role played by hyperbaric oxygenation in these experiments was difficult to asses but hyperbaric oxygenation has beneficial effect on renal preservation and limitation of preservation time was considered between 12 and 24 hours.