Peripheral auditory sensitivity is documented over a 5-year period on 4 cases with otodental dysplasia. Age of onset is noted for the proband and indicates that onset of this progressive hearing loss occurs as early as the first decade. Findings suggest that the hearing loss plateaus by the fourth decade, resulting in a severe, flat, bilaterally symmetrical sensorineural hearing loss. The audiometric configurations are similar in all affected members of the kindred evaluated. Speech discrimination scores of the observed magnitude are somewhat uncharacteristic for the type and degree of impairment observed. Differential diagnostic audiometric test results suggest a cochlear site of lesion.