Bretylium tosylate (BT), an antifibrillary drug, was found to potentiate the taste of NaCl and LiCl in both humans and rats. Application of 1 mM BT (pH 6.3) to the human tongue statistically potentiated the taste of 0.2 M NaCl and 0.2 M LiCl by 33.5% and 12.5% respectively. Electrophysiological taste responses from nucleus tractus solitarius (NTS) in rat for both hyposmotic and hyperosmotic concentrations of NaCl and 0.1 M LiCl were also increased by 30 to 40% after application of 1 mM BT. This potentiation induced by BT was reduced by amiloride in both humans and rats. Furthermore, amiloride became ineffective in inhibiting taste responses to NaCl in the presence of BT.