Hearing loss is the most frequent sensory defect in humans. Dozens of genes may be responsible for the early onset forms of isolated deafness and several hundreds of syndromes with hearing loss have been described. Both the difficulties encountered by linkage analysis in families affected by isolated deafness and the paucity of data concerning the molecular components specifically involved in the peripheral auditory process, have long hampered the identification of genes responsible for hereditary hearing loss. Rapid progress is now being made in both fields. This should allow completion of major pieces of the jigsaw for understanding the development and function of the ear.