Abstract: A modification of the experimental apparatus widely used in our country for evaluating antitussive agents in mice was made. The important points of modification include:(a) by using compressed air passing through an arterial cannula, ammonia gas was used instead of ammonia aerosol to induce cough;(b) a large glass chamber was used in place of a small glass chamber for holding the mice.With the modified apparatus, the EDT₅₀ of the control animals and the effective dose of codeine phosphate for controlling cough are all similar to those obtained with the original method. The main advantage of the modified apparatus as compared with the original one is twofold, namely, simpler in construction and easier to operate.