The thresholds of the pH for citric acid (pH=4.9) were found to exceed by 1.4 pH the thresholds for HC1 (3.5) at 1.2 mmol/1 bicarbonate in the solution. The reaction to citric acid was higher than to HC1 at equal pH. Decreasing of bicarbonate from 1.2 mmol/1 to 0 reduced pH threshold only for sitric acid from 4.90 to 3.15. pH threshold for HC1 remained 3.5 The chorda tympani response to stimulation with solutions containing bicarbonate (1.2 mmol/1) was higher than in absence of bicarbonate. The data obtained suggest two ranges of the acids in action.