Progress in the Human Genome Project, availability of cochlea-specific cDNA libraries, and development of murine models of deafness have resulted in rapid discovery of many loci and corresponding genes for deafness. Up to now, the chromosomal locations of about 70 genes for non-syndromic deafness have been mapped, and the genes of more than 20 loci have been identified and characterised. Mutations in one gene, connexin 26 (CX26GJB2), are responsible for most cases of recessive non-syndromic deafness, accounting for 30-40% of all childhood genetic deafness in some populations (eg, white people of western European descent). We summarise advances in identification of genes for deafness and provide a guide to the clinical approach to diagnosis of patients with hearing loss.