AbstractCardiovascular responses to carotid body chemoreceptor stimulation were followed in the ‘curarized’, vagotomized, artificially ventilated cat. Stimulation of the chemoreceptors by perfusion of the carotid sinus regions with venous blood induced a reflex vasoconstriction in skeletal muscle, kidney, intestine and skin, and, in most cases, an increased heart rate. A comparison of the chemoreceptor reflex responses with those obtained by direct electrical stimulation of the regional vasomotor fibres indicated that in chemoreceptor reflexes the vasomotor fibre activity increased to the same extent in skeletal muscle and intestinal resistance vessels and, probably, in the ‘nutritional’ skin vessels but to a smaller extent in the renal vessels and the skeletal muscle capacitancc vessels. The renal vessels and the muscle capacitance vessels seemed, however, to respond more during chemoreceptor stimulation than when the baroreceptors were unloaded, indicating that an excitation of the bul bar vasomotor centre is more effective than the withdrawal of an inhibitory restraint in activating the vasomotor fibres to these vascular s