During the past two decades considerable progress has been made in understanding the neurophysiological changes that occur in the peripheral and central auditory pathway as a result of sensorineural hearing loss (SNHL). SNHL does not simply cause a loss of sensitivity, but instead produces a complex set of changes in the way the auditory system processes sound information. In addition to the loss of sensitivity, the most prominent deficits seen in the periphery include a loss of frequency selectivity, two-tone suppression and distortion products responses. Although the primary site of damage appears to be in the cochlea, a multitude of unexpected functional changes occur in the central auditory pathway including enhanced evoked response amplitudes, loss of inhibition, hypersensitivity to electrical stimulation, loss of temporal integration and reorganization of the tonotopic map.