Genetic analysis of hereditary deafness (HD) has been performed in the city of Kirov and ten rural districts of Kirov oblast (administrative region). The analysis employed the methods used in audiology, medical genetic counseling, and DNA diagnosis. Deafness has been established to be hereditary in 143 children from 100 unrelated families. The incidence rates of isolated and syndromic HDs in the period studied (1995-2001) have been estimated at 1.25 and 0.36 per 1000 newborns, respectively, the total incidence rate of all HD forms being 1.61 per 1000 newborns (1 case per 621 newborns). DNA analysis for the detection of seven frequent mutations in the genes GJB2 (the 35delG, 167delT, 235delC, and M34T mutations), GJB6 (the del(GJB6-D13S1854) and del(GJB6-D13S1830) mutations), and TMC1 (the R34X mutation) has been performed in families with isolated neurosensory deafness. Molecular genetic analysis has detected mutations in 51 children (48.6%); in 54 children (51.4%), no mutations have been found. The following genotypes have been identified in children with HD: 35delG/35delG in 32 probands (30.5%), 35delG/+ in 16 probands (15.2%), 35delG/235delC in 1 proband (0.95%), M34T/+ in 1 proband (0.95%), and M34T/35delG in 1 proband (0.95%). The 167delT mutation has not been found. The frequency of the 35delG mutation in the GJB2 gene has been estimated to be 39.05%. In the group with a family history of HD, mutations have been found in 66.7% of patients; in the group without a family history of HD, in 37.5% of patients. No mutation has been found in the GJB6 or TMC1 gene. Molecular genetic analysis has been performed in a family with clinically diagnosed Treacher Collins-Franceschetti syndrome. Sequencing has been used to find the 748-69C>T polymorphism in intron 6 (in the homozygous state) and the 3635C>G mutation in exon 23 leading to the substitution of glycine for alanine at position 1176 of the amino acid sequence (Ala1176Gly, in the heterozygous state), which have not been described before.