Cochlear nerves of 11 patients with advanced Meniere's disease were studied by light and electron microscopy. All the nerves appeared normal on light microscopy. In cross sections, the density of myelinated nerve fibers was approximately 20,000 fibers per square millimeter in most cases. In two cases, the density was reduced, about 14,000/sq mm. No correlation was found between the age of patients or the duration of the disease and the density of myelinated nerve fibers. On electron microscopy, there were several features that suggested primary axonal degeneration or segmental demyelination in the cochlear nerve.