Functional changes in the kidney exposed to 1-hour ischemia with surface cooling to +5+7 degrees C (series I) or +16+18 degrees C (series II) were studied in experiments on 50 rabbits and 20 non-inbred rats. In series II animals significant changes in renal function were not registered. In series I cooling there was a marked decrease of creatinine clearance, clearance of osmotic substances and Na-reabsorption during 1-3 days after ischemia. Dynamic scintigraphy with 131I-hyppuran revealed a decline in radionuclide secretion in series I that was more pronounced on day 14. In series II the time course of accumulation and excretion of 131I-hyppuran was almost normal. The worsening of renal function in series I experiments was accompanied with reduction of renal blood flow and activation of cell membrane lipid peroxidation. The investigation of the dependence of renal tissue impedance on the temperature that reflects thermotropic response of cell membrane structural organization showed phasic transitions of membrane lipids at the temperature below +13+14 degrees C. The findings indicate that for prolonged discontinuation of renal blood flow demanding deep kidney cooling, it is necessary to develop specific measures of protection against detrimental action of hypothermia.