The ultrastructural pathology in an ear with long-standing profound deafness is presented. Endolymphatic hydrops was present, although there had been no vestibular symptoms. Although hair cells were absent, the intercellular junctional complex at the endolymphatic surface of the organ of Corti was maintained, suggesting "healing" by migration or proliferation of supporting cells to fill the empty spaces. Severe atrophy of the stria vascularis was present, and crystalline deposits were found within the strial remnant. An encapsulated tectorial membrane was interpreted in light of ultrastructural findings as either herniation of the fibrillar connective tissue of the spiral limbus into the scala media or alternatively demonstrating abnormal continuity between the connective tissue of the spiral limbus and the remnant of tectorial membrane. Neural degeneration was severe in all cochlear turns. However, more nerve fibers were seen in the proximal portion of Rosenthal's canal than at the habenula perforata or in the organ of Corti, and central processes from the ganglion area were more numerous than peripheral processes. The ganglion cell population was reduced to approximately 10% of normal, and only unmyelinated cell bodies were found. Few recognizable neural fibers were seen within the organ of Corti, although bizarre collections of apparent cellular debris and cell processes containing many mitochondria or vesicles were seen in regions normally containing neural fibers.