Analysis of insertion-deletion polymorphism of serotonin vector gene (SLC6A4) was carried out in Russian and Tatar men with acute alcoholic psychosis. Significant interpopulation differences in the distribution of SLC6A4 genotype and allele frequencies were revealed. A relationship of L/S gene with the disease was detected in Russians and Tatars, but the presence of heterozygotic genotype was associated with early onset of chronic alcoholization and development of acute alcoholic psychosis in Tatars and with later alcoholization and disease development in Russians. The share of S/S genotype was significantly decreased in Russian patients aged over 35 years, which suggests selection aimed at elimination of short allele homozygotes among patients with this disease and probably different genetic prerequisites for early and late development of the disease in Russians. In Tatars aged over 35 years acute alcoholic psychosis is associated with L/L genotype (RR-3).