Specific antibodies raised against human cerebellar calcium-binding protein (CaBP) intensely labelled the cochlear hair cells of the rat. The vestibular hair cells also stained weakly. In both inner and outer cochlear hair cells, the cuticular plate was the most stained area. These results suggest that CaBP may prevent excessive concentrations of intracellular calcium and thus modulate some Ca2+-mediated biochemical processes, especially at the level of the cuticular plate and stereocilia; CaBP could be involved in the mechanochemical coupling of hearing or vestibular function.