1. Certain afferent fibres in the renal nerves show an increased rate of discharge in response to small increases in renal vein pressure and to substantial increases of ureteral pressure. Such fibres enter the spinal cord largely through the upper lumbar dorsal roots.2. In spinal cats, stimuli exciting these afferent fibres evoke a reflex discharge in sympathetic nerves to the kidney and a fall in systemic arterial pressure. Change in flow or peripheral resistance, independent of arterial pressure, could not be demonstrated for the renal vascular bed. In spite of a lack of evidence for a renal vasomotor effect, the existence of the reflex fall in arterial pressure following excitation of receptors sensitive to venous pressure strongly implies that there is a form of circulatory regulation at the spinal cord level.