Two-hundred and forty White children attending special schools for the deaf have been investigated by clinical,genetic and laboratory methods in order to determine determine the aetiology of their hearing disability of these, 36% had a genetic basis for their deafness, while in a further 34% an acquired lesion was incriminated. The most important determinants of acquired deafness were maternal rubella, neonatal hyperbilirubinaemia and meningo-encephalitis. The prevention of childhood deafness is primarily dependent upon recognition of the underlying causative factor.