Regeneration of the neurosensory structures in the mammalian inner ear. Motivated by the absence of treatment of neurosensory deafness apt to restore auditory function or alter the course of progressive hearing loss, we developed two different experimental strategies to approach these diseases: one is otoprotection, designed to prevent further degradation of auditory function; the other is regeneration which is defined as the replacement of hair cells in the deaf ear and their reconnection to the central nervous system through primary auditory neurons. In this paper, we summarize our data on the regeneration of auditory neurons and hair cells. Neuronal maintenance and regeneration was studied through an initial investigation of growth factors during inner development. Once the effect of various neurotrophic molecules was determined, the factors were tested on mature auditory neurons in vitro and in vivo. The hair cell regeneration was investigated on the basis of a concept derived from comparative physiology and from the study of the development of the inner ear. We showed that in young rats it is possible to induce the regeneration/repair of hair cells in the organ of Corti in cultures using retinoïc acid and transforming growth factor alpha. The clinical prospects of these findings of inner ear regeneration are discussed.