The aim of the study was to elucidate the causes of hereditary non-syndromic loss of hearing, a frequent monogene pathology in the Republic of Sakha (Yakutia). A search for mutations in the coding sequence of the connexin 26 gene gap-junction B2 (GJB2) was undertaken in 79 members of 65 unrelated families with the diagnosis of grade III-IV non-syndromic bilateral sensorineural loss of hearing. Five recessive mutations (35delG, V371, 312-326del14, 333-334delAA, R127H) and three polymorphic variants (V271, M34T, E114G) were identified in Yakut patients. Mutations 35delG (41.7%), 312-326dell4 (4.2%), and 333-334delAA (4.2%) were found in Caucasian patients (Russians, Ukrainians, Inguish). Yakuts were carriers of mutations 35delG (2.1%), V371 (2.1%), R127H (1.0%) and sequence variants V271 (6.3%), M34T (1.0%), E114G (1.0%). GJB2 mutations were identified in 50.1% of the Caucasian patients and in 7.2% of the Yakut patients. The low frequency of GJB2 mutations in Yakuts with non-syndromic sensorineural loss of hearing testifies to the presence of mutations of other genes controlling sound perception in this population.