The aim of this work was a clinical study of the patients with mutations in the SLC26A4 gene and clinical diagnosis of the Pendred syndrome. The Pendred syndrome is a hereditary autosomal recessive disorder characterized by combined pathology of the inner ear and the thyroid gland. CT of the temporal bones demonstrates the Mondini-type structural anomaly in the inner ear and enlarged vestibular aqueduct. Examination of the thyroid gland reveals hypothyroidism and euthyroid goiter. A total of 20 unrelated children at the age from 2 to 16 years presenting with the hearing loss of different severity were available for the examination. High-resolution CT of the temporal bones demonstrated abnormal development of the inner ear including the Mondini-type structural anomaly and enlarged vestibular aqueduct. Five children with congenital hypothyroidism suffered from bilateral sensorineural impairment of hearing. The routine methods of audiological and molecular genetic examination were used throughout the study. Results. As a result of molecular genetic studies, four out of the 20 patients were found to carry six recessive mutations of the SLC26A4 gene in the compound heterozygous and one such gene in the homozygous state which confirmed the hereditary nature of the disease. The children suffered the hearing loss of varying severity diagnosed at different age. The thyroid hypofunction in one child was identified when it was 2 years of age, and in two children at the age of 8 and 9 years. Conclusions. The first step in the diagnosis of the Pendred syndrome among children with congenital hearing loss was a CT scan of the temporal bones that showed incomplete separation of the curls of the cochlea and enlarged vestibular aqueduct. It is necessary to continue to study epidemiology, clinical and molecular genetics of the Pendred syndrome in the Russian population.