Results of experimental studies with guinea pig showed that a strong blast may produce concussion of the vestibular apparatus. The parts injured include saccule and utricle and their maculas, semicircular canals and their cristas,and the nerves related to these organs.The most common pathological changes were hemorrhage, detachment of sensorial epithelium, collapse of membranous labyrinth, loss of oto-liths and degeneration of sensorial epithelial cells.The authors believe that these vestibular damages are produced by the combined action of strong noise and shock wave, being transmitted through the oral and round windows into the inner ear, producing a violent fluctuation of endolymph.