Keratin distribution in cochlear cells has been studied immunoelectronmicroscopically by both pre-and post-embedding methods. Keratin immunoreactivity in guinea pig cochlea was distinctly demonstrated in: Hensen's cell, reticular laminae surrounding both outer and inner hair cells, outer and inner pillar cells, Claudius' cell, inner and external sulcus cells, interdental cell of spiral limbus, Reissner's membrane, border cell, inner phalangeal cell, Deiters' cell and spiral prominence cell. Keratin expression at ultrastructural level showed a non-filamentous keratin system in the cytoplasm of cochlear supporting cells. It may be an interesting approach for further study.