The innervation densities, i.e. the number of afferent endings per inner and outer hair cell, number of synaptic specializations per inner hair cell and the number of efferent endings per outer hair cell, were evaluated by serial section electron microscopy in the normal human inner ear and a case of Usher’s syndrome (retinitis pigmentosa and sen-sorineural hearing loss). There was a significant decrease in the innervation density in Usher’s syndrome as compared to normative controls, which could not be explained by the decrease in density of spiral ganglion cells. This was interpreted as suggesting a decrease in the number of neural processes and endings within the dendritic arborization of remaining spiral ganglion cells in this disor