The histopathologic findings in the temporal bones of two patients who underwent a cryo-otic-perotic shunt procedure are reported. Morphologic changes in the inner ear were limited to the area of cryoprobe application on the promontory. The hook region of the cochlear duct showed severe atrophy of the spiral ligament, stria vascularis, and sensorineural structures. The ampulla of the posterior semicircular canal showed fibrosis in the perilymphatic space and ruptured membranous walls.No changes were found in the rest of the vestibular labyrinth or in the facial nerve. The long-term improvement in these patients' symptoms, i.e., eight years in one and four years in the other, could only be explained on the basis that endolymph and perilymph mix across intact, nonfunctioning membranes of the cochlear duct or through, presumably antemortem, ruptures of the posterior semicircular canal ampulla.