The author observed temporary threshold shift of hearing after the exposure of the pure tone stimuli on 10 ears with normal hearing. The sound stimulation was performed with 1000 cps and 3000 cps, and these frequencies were emitted at 30db and 90db above the threshold for 2 minutes. The threshold shift was checked after the cessation of stimulation with the intervals of 15 seconds for first 30 seconds, 30 seconds for next 90 seconds, and every one minute thereafter. The following results were obtained; 1) The poststimulatory fatigue stimulated with 30db was not less than on the case with 90db. 2) The post stimulatory fatigue depended on frequency of stimulus, the 3000 cps being more fatigued than 1000 cps. 3) Fatigue was not limited to the threshold of stimulated frequency. With the fatiguing sound of 30db in 1000 cps, the fatigue was appeared on stimulated frequency more than other frequencies and spreaded out equally on the lower and higher tones, but in 3000 cps, fatigue increased on one half octave above the stimulated frequency. For sounds of 90db above the threshold, fatigue decreased very rapidly on the lower frequency below the stimulated tone, and markedly increased on the higher tone above the stimulated tone. 4) The poststimulatory fatigue varied from individuals and ears of the same person.