BACKGROUND AND OBJECTIVE: Hearing impairment is the most common sensory defect in human beings this highly heterogeneous disorder affecting 1 in 1000 among general population that half of them is due to genetic agents. Albeit, this frequency in Iran is higher than other countries and it needs to pay more attention to this condition. Ear acts as a connector between human and environment hearing process is composed of a series of complex events thorough the ear so that sound waves lead to physical vibrations in inner ear producing electrical signals. This signal is processed within the hearing regions in two sides of the brain. Sensorineural hearing loss (HL) is classified into acquired HL, genetic HL and deafness of unknown origin. If other than deafness, other problems occur in affected individuals, HL is belonged to syndromic form of deafness while in many cases, hearing loss occurs without any other problems.

 METHODS: In this study, mechanisms of hearing, various types of hearing loss and genetics studies in Iran in comparison with other population of the world are investigated and reviewed.

FINDINGS: GJB2 mutations are the most common cause of autosomal recessive non-syndromic hearing loss (ARNSHL) in most populations and even up to 50% of ARNSHL in some cohorts is due to these mutations. GJB2 mutation frequency is 14-17% among Iranian populations. More than 90% of genetics studies of HL have been performed on GJB2 mutations. However, there are some reports about other loci involving in HL.

 CONCLUSION: Mutations in more than ten genes lead to ARNSHL in our country that GJB2 has more important role than other genes. It showed GJB2 connexin 26 in Iran