Remarkable progress has been made in the past decade in identifying genes involved with deafness in man and mouse. The identification of these genes and functional analysis of the proteins they encode are paving the way towards a better understanding of the physiology and pathophysiology of the auditory system. Given the complexity of auditory transduction and diversity of cochlear structures, it is not surprising that an estimate of at least 1 percent of human protein-coding genes are involved in perception of sound. Over 400 distinct syndromes of which hearing loss is a component have been reported (www.ncbi.nlm.nih.gov/omim). Approximately 113 loci for monogenic disorders for which hearing loss is the only manifestation and therefore is nonsyndromic, have been mapped to the human genome (http:webhost.ua.ac.be/hhh/). As of August 2007, there are approximately 46 genes identified from these loci. Here, we review some of the major advances in our knowledge of auditory function within an evolving understanding of the structure and regulation of the machinery of hearing.