The total blood flow of rabbit's ear was inversely proportional to ambient temperature when the hypothalamic temperature was by 1 +/- 1.5 degrees C higher than normal due to ambient temperature raise from 15 degrees to 35 degrees C. The data obtained corroborate the viewpoint that the blood flow regulation not only controls heat loss by the rabbit ear, but also stabilizes the temperature of venous blood flow in the ear, when the ambient temperature varies in wide range.