Polymorphism of the serotonin transporter gene (hSERT) was studied in eight human populations of the Volga-Ural region by means of polymerase chain reaction (PCR). The populations studied belonged to Turkic (Bashkirs, Tatars, and Chuvashes), Finno-Ugric (Maris, Komis, Mordovians, and Udmurts), and Eastern Slavic (Russians) ethnic groups. Comparison of the hSERT polymorphisms in these populations established the population-specific distribution patterns of the main component of this polymorphic system in the region studied and revealed the interethnic differences in hSERT allelic and genotypic frequencies.