Lingual application of amiloride hydrochloride blocks a sodium transport system in the mammalian gustatory system. Effects of exposure to amiloride on subsequent licking for 3% NaCl by rats were found to differ as a function of the animal's sodium balance. Licking for 3% NaCl was significantly increased in sodium-replete rats and significantly decreased in sodium-deplete rats by amiloride pretreatment. In fact, expression of sodium appetite was virtually eliminated by pretreatment with amiloride. This suggests that the recognition of sodium solutions in animals with a sodium deficit is dependent on amiloride-sensitive sodium transport at the taste bud.