Damage and loss of hair cells in the inner ear is the most frequent cause of hearing loss (HL), since mammalian hair cells are not replenished once lost. To date, the treatment of HL consists of hearing aids or cochlear implants, but both options restore hearing with limited success. Gene therapy is an attractive option as a means for treating sensorineural hearing impairment, although at present it is investigational. The finding that hair cells can regenerate in nonmammalian vertebrates has triggered many studies, with the hope of simulating a similar process in humans. Current research that focuses on the auditory pathways, the genes involved in HL, efficient ways to transfer therapeutic agents into the inner ear, and optimization of gene manipulation, gene therapy, and stem cell treatment raises hope for restoring hearing and curing deafness.