For the purpose to find out the effects of sound stimulation not only on the organ of hearing but also on all the other organs of the body, changes in serum vitamin A were determined by the CarrPrice reaction test giving pure tone and thermal noise to healthy rabbits. Results ob tained were as follows:1. Changes, particularly a marked decrease in serum vitamin A due to sound stimulation were observed.2. In the case to which stimulation was given for a short period, however, serum vitamin A showed a gradual decrease after showing a transient increase. On the other hand, when the hearing organ was stimulated for a long period, serum vitamin A decreased at once without showing transient Increase.3. Regardless to the nature of stimulating sound, stimulation by sound of a great intensity produced a decrease in serum vitamin A. The longer the stimulation time was, the more remarkable was the decrease; therefore, the recovery time was delayed.4. A decrease in serum vitamin A due to sound stimulation was inhibited by sympathetic blocking agents to a certain extent.