The diversity of Mendelian hereditary pathology has been studied in Sakha Republic (Yakutia). The sample comprised 1 000 700 subjects, including 363 316 Yakuts, 14 428 Evenks, 8668 Evens, 550 263 Russians, and 64 025 subjects from other ethnic groups. Fifty-one autosomal dominant (AD) diseases, including five diseases with frequencies of 1 : 50 000 or higher; 40 autosomal recessive (AR) diseases, including eight diseases with frequencies of 1 : 50 000 or higher in the Yakut population; and five X-linked diseases have been detected.