To study auditory and vestibular disorders following chronic perilymphatic fistula, we inserted a small tube into the scala tympani of the basal turn of the cochlea of guinea pigs. For observation of nystagmus in the guinea pig, specially fashioned Frenzel's glasses were used. Histopathological examination was done one month after the perilymphatic fistula was made. Our results showed the existence of directional preponderance of post rotatory nystagmus with corresponding endolymphatic hydrops, hair cell damage and partial injury to the vas spirale around that hair sell damage. We suspect that some reduction in the blood supply resulted in hair cell destruction.