Aminoglycosides antibiotics have been used systemically or topically for a medical treatment of the intractable vertigenous Meniere's disease. Recently topical administration of the streptomycin to the lateral ampulla was attempted to the Meniere's patients for the unilateral destruction of the vestibular system, however, there are some criticisms for the introduction of a new treatment modality without basic pathophysiologic workup. To enforce and clarify the weak pathophysiologic background, streptomycin sulfate soaked gelfoam was applied to the artificially made fistula on the lateral ampulla. The animals were sacrificed at the third, seventh, tenth, and fourteenth day after drug application respectively, and the morphological changes of the vestibular sensory organs were studied by transmission and scanning electron microscope. Three days after the streptomycin application, degenerative changes were found in the type I sensory cells in the central region of the cristae and macula utriculi. The degenerative changes were the loss of the sensory cilia, cytoplasmic protrusion, pyknosis, and the loss of inner septa of the mitochondria in the supranuclear portion. Seven days after drug application, almost all type I sensory cells were disappeared in the three cristae and the only degenerated type II sensory cells were partly remained in the peripheral region of the cristae and macular utriculi, however, the sensory cells in the saccula maculi were remained intact. Ten days after the drug application, almost all sensory cilia were disappeared in the three cristae, and the numerous globular masses were scattered on the endolymph surface. The type I and II sensory cells were disappeared and the supporting cells were replaced where the sensory cells were located. A part of the supporting cells showed cellular degeneration. The changes of the macula utricli were less severe than the cristae, and the sensory cilia were remained intact in the peripheral region from the striola. Fourteen days after drug application the globular masses were embeded into the degenerated thin cupula. Slender and bended sensory cilia which probably originated from the remained or regenerated type II sensory cells were found under the degenerated cupula in the three cristae. However, even severe destruction of the macula utriculi, the sensory cells of the macula sacculi still remained intact. Compared to the systemic administration, streptomycin application on the lateral ampulla can efficiently destruct the sensory cells of the cristae with saving the sensory cells of the macula sacculi in a relatively short time. Intact macula sacculi suggests preservation of the cochlea sensory cells due to penetration of the drug to the cochlea by passive diffusion through the ductus reuniens. However, the remained or regenerated sensory cilia and type II sensory cells in the crista and the macula utriculi suggest complete destruction of the vestibular labyrinth couldn't be achieved by single application of the streptomycin on the lateral ampulla.