Bovine adrenals were perfused with secretagogues in the presence or absence of muscle relaxants. On a molar basis, Dially-nor-toxiferine was as potent as tubocurarine in inhibiting the catecholamine release induced by carbachol; pancuronium was about 100 times less potent than tubocurarine, whereas gallamine and succinylcholine produced no inhibition whatsoever. KCl-induced catechoamine release was not affected by any of these compounds. Nicotine-induced catecholamine release was inhibitedby diallyl-nor-toxiferine, tubocurarine and pancuronium, but not by gallamine or succinylcholine. Muscarine failed to stimulate the adrenal medulla to release catecholamines. The results show that the inhibition of catecholamine release is based on the specific block of the nicotinic receptor, whereas gallamine and succinylcholine possess no blocking action, and that diallyl-nor-toxiferine and tubocurarine might affect clinical symptoms under conditions in which catecholamine release from the adrenal is increased by a compensatory mechanism.