Abstract: A modification of the screening apparatus for evaluating the actions of antitussive agents in mice was reported in the present paper. The principal modification is to change the aerosol of ammonium hydroxide into the inhalation of ammonium vapor. A suction was attached to the apparatus instead of an air compresser, so the glass aerosol device was omitted. In addition to the advantages of the original method, the modified apparatus has the following properties: (a) higher availability for materials and appliances; (b) simplification of equipment; (c) convenience to operate; (d) easy control of conditions; and (e) harmlessness to experimenter's health.