With the purpose to determine the pothological changes occurring in the peripheral auditory organs in the animals administered various doses of dihydrostreptmycin, with a special reference to the changes in the spiral ganglion cells, as well as to study the progress after the acute poisoning induced by this drug, the author conducted the present experiments using three groups of guinea pigs, namely, one group inecjected with a large dose of 300 mg dihydrostreptmycin (DHSM) per day, another group injected with an intermediate dose of 200 mg, and still other with a minimal dose of 100 mg. For the investigation of nerve cells the author excised only the modiolus by breaking the cochlear bony shell with a bar and an incision needle under a bright field of binocular microscope and fixed it after one day's decalification. This method employed by author proved to be significantly satisfactory for the determination of the pathological changes in nerve cells. Histopathological changes 1. When DHSM is injectid intramuscularly, pathological changes are induced in the peripheral auditory nerve, namely, organ of Corti, cochelear nerve fibers and spiral ganglions, but the greatest injury appears in the organ of Corti, especially in inner and outer hair cells. 2. These pathological changes are more marked at the base of the spiral and they grow less severe nearer to the end of the spiral. 3. This method of observing pathological changes of the spiral ganglions by modiolus method greatly improves the accuracy in the determination of such changes, and for this reason it is believed this method to be of a great significance. 4. These pathological changes are considered to be the cause of deafness. 5. The severity of pathological changes does not necessarily parallel with the doses of the drug administered and this seems to be due to some individual differences in the resistance against the drug. 6. As there occurs a degenerative atrophy of the end organs as well as spiral ganglion cells and nerve fibers in the inner ear of those animals either staving or emaciated, it is advisable to exclude those animals that lost more than 20-30 percent of the body weight from such experiment. 7. These pathological changes showed no tendency to recover spontaneously.