Congenital deafness has the heterogeneous nature and can be underlain by both acquired and genetically determined causes. It has been estimated that the prevalence of clinically manifest forms of congenital deafness amounts to 1 case per 700 births. Half of these patients present with the deafness of genetic origin. One of the most common forms of congenital deafness is the hereditary one associated with mutations of the GJB2 gene. The most frequent mutation documented in this country is 35delG leading to congenital and prelingual bilateral deafness in 52% of the cases. The number of carriers of the 35delG mutation among healthy populations in the majority of regions of the Russian Federation is estimated at 2-4%. At present, identification of a child with bilateral loss of hearing in the course of detailed audiological screening dictates the necessity of genetic testing. It is believed that combined audiological and molecular genetic screening may be helpful for the early detection of children with a pathological genotype including those with only slightly manifest hearing loss at birth. Families having such a child should be in due time counseled about the risk of giving life to another child with the above disorder by the same couple or other relatives of the childbearing age.