The values obtained by means of the electromagnetic flowmeter technic are in good agreement with those obtained by Kety''s nitrous oxide method. Kety''s values for the total cerebral circulation are 740 cc per minute or 54 cc per 100 g of brain tissue per minute. The blood flow through the common carotid artery as measured with our technic is about 500 cc per minute, with about 350 cc passing through the internal carotid artery and 150 cc through the external carotid artery. Our values are somewhat lower than those given by Kety, but, considering the blood flow through the vertebral arteries, our measurements seem to give somewhat larger values for the total circulation to the brain than the measurements of Kety. The electromagnetic flowmeter method permits a selective study of the blood flow through different arteries. It may be a valuable adjunct in the clinical and radiologic evaluation of patients with vascular disease of the brain, as well as an excellent tool for obtaining data concerning the normal circulatory physiology of this important vascular bed.