Abstract: The effect of Schizandra chinensis Baillon on the higher nervous activity of the dog was studied with the conditioned reflex method in a specially constructed soundproof chamber. A positive reflex of salivary secretion was established on condition that the dog was given the metronome sound (80/min) as a conditioned stimulus and the food, an unconditioned stimulus (reinforcement). By means of stopping repeated reinforcement, the effect of the aqueous extract of the drug on conditioned stimuli might be tested in order to investigate how far the extinction would be influenced. It was found that the effect of the drug depended chiefly on the dosage and the stability of the extinctive inhibition in the test. A dose of 0.03 g/kg of the drug diminished the extinctive inhibition at the early stage of extinguishing, as shown by delaying the appearance of extinction. A similar but unstable effect was obtained with a dose of 0.05g/kg, and the extinctive inhibition was strengthened with doses of 0.1-0.2 g/kg, as shown by the earlier appearance of extinction. However, once the extinctive inhibition was firmly established, there was no effect even with the large doses. With smaller doses, the drug behaved like caffeine, but was weaker.