Three-day old chicks were given kanamycin at a dose of 200 mg/kg/day for 10 days and their cochleae were processed for scanning electron microscopy at 1, 3, 7 and 14 days following the last injection. Both hair cells and supporting cells were damaged by kanamycin in the basal 35% of the basilar papilla. By 14 days post-treatment, however, most of the damaged region had been replaced with regenerating hair cells and supporting cells. The base-to-apex gradient of morphological development along the cochlea was observed in the process of regeneration. Kinocilium and microvilli were observed on the apical surfaces of the regenerating hair cells.