Genetic and auditory studies of 731 children with severe-to-profound hearing loss in US schools for the deaf and 46 additional children receiving clinical services for hearing loss ranging from moderate to profound demonstrated that mutations in the connexin 26 (GJB2) and connexin 30 (GJB6) genes explain at least 12% of those with nonsyndromic sensorineural deafness. Otoacoustic emissions (OAEs) testing to detect functional outer hair cells indicated that 76 of the children had emissions and therefore may have (as yet unconfirmed) auditory neuropathy/dys-synchrony (AN/AD). Five of these children with OAEs were GJB2 homozygotes or compound heterozygotes with the genotypes 35delG/35delG, W77X/W77X, 35delG/360delGAG, 35delG/V95M, and V84M/M34T. In particular, unilateral AN/AD was confirmed in a child with moderate hearing loss and the 35delG/V95M genotype. Detecting OAEs in individuals with GJB2 mutations suggests that lack of functional gap junctions as a result of GJB2 mutations does not necessarily destroy all outer hair cell function.