The diuretic amiloride, a potent inhibitor of sodium transport in a variety of epithelial systems, was applied to the human tongue. Application of amiloride reduced the taste intensity of sodium and lithium salts and of sweeteners ranging widely in chemical structure. The sweeteners included saccharides, glycosides, dipeptides, proteins, and amino acids. Amiloride did not affect perception of potassium or calcium salts, bitter and sour tastes, or amino acids without a sweet or salty component. These findings were supported by neurophysiological studies in rat, which showed that amiloride diminished the NaCl response relative to KCl. The results are consistent with the position that an amiloride-sensitive transport mechanism is involved in taste perception of sodium and lithium salts and of sweeteners.