The past decade has seen extremely rapid progress in the field of hereditary hearing loss. To date, 80 loci for nonsyndromic hearing loss have been mapped to the human genome. Furthermore, 30 genes have been identified. These genes belong to a wide variety of protein classes: from myosins and other cytoskeletal proteins, over channel and gap junction components, to transcription factors, extracellular matrix proteins and genes with an unknown function. The identification of these genes has enabled geneticists to offer DNA diagnostic tests for some types of nonsyndromic hearing loss. Moreover, it holds the promise to significantly improve the molecular knowledge on the auditory and vestibular organs and on the pathological mechanisms leading to hearing loss. This opens perspectives for future therapeutic and/or preventive measures for hearing loss. This review attempts to give an overview of the current knowledge of the genes responsible for nonsyndromic hearing loss, their expression and functions in the cochlea.