Renal function was measured in seven normo thermic (38 degrees C) and seven hypothermic (27 degrees C) dogs. 2. The glomerular filtration rate was 60 per cent lower in the hypothermic animals, and the renal blood flow as 51 per cent lower. The intrarenal distribution of blood flow was measured by the uptake of 86Rb from the blood into different regions of the kidney. Hypothermia reduced flow by 34 per cent in the outer cortex, 72 per cent in the inner cortex, 61 per cent in the outer medulla and 69 per cent in the inner medulla. 3. Radioautography indicated a high blood flow to an area of the outer medulla of hypothermic kidneys, which may indicate medullary blood flow "shunting". 4. The results have been discussed in relation to a number of clinical and experimental observations.
