The recent widespread interest in the action of tetraethyl ammonium ion as the result of the work of Acheson with Moe1and Pereira2in demonstrating its selective blocking of transmission of impulses across sympathetic ganglions has led to its clinical trial in a wide variety of vascular disease. We,3as well as Lyons and associates,4have been particularly interested in its action in hypertensive patients, and it is with these that this communication is concerned. Epinephrine ("adrenalin" N. N. R.) has been recommended as the antidote of choice after excessive doses of tetraethyl ammonium chloride. Acheson and Moe1have shown that in cats with spinal block induced by this drug the response to epinephrine was at least unaffected. During the course of experiments to determine the effect of tetraethyl ammonium chloride on the blood pressure of hypertensive dogs, there was occasion repeatedly to test the