The carotid chemoreceptors of narcotized, vagotomized and spontaneously breathing hydropenic cats in hypertonic mannite diuresis were stimulated by perfusion with venous blood penic cats in hypertonic mannite diuresis were stimulated by perfusion with venous blood for 70 min. Elevation of blood pressure at the innervated kidneys was prevented by an automatically controlled balloon located within the aorta. Stimulation of the chemoreceptors intensified respiration and raised the arterial systemic pressure. With the renal arteries at constant pressure, the effective renal plasma flow and the glomerular filtration rate significantly declined. The filtration fraction remained unchanged. The absolute urinary and sodium excretion did not change significantly, whereas the fractional time-volume, fractional sodium excretion, and the fractional osmotic excretion significantly increased. The fractional tubular reabsorption of osmotically free water was significantly enhanced. These reactions subsided during subsequent perfusion of the glomerula carotici with arterial blood. The results suggest that tubular sodium reabsorption is inhibited by stimulation of the carotid chemoreceptors, although re-adjustment of renal perfusion and filtrate volume cannot be excluded.