The analysis of Msp1 polymorphism (-1438G/A) in the promoter region of serotonin receptor type 2A (5HTR2A) gene has been conducted using polymerase chain reaction method in the men with an acute alcoholic psychosis of Russian and Tartar nationalities. The results obtained indicate the 5HTR2A gene is involved in development of the given pathology and allow to conclude that (1) 5HTR2A genotype's and allele's frequency distributions in Russians and Tartars do not significantly differ and correspond to those for the white Americans; (2) for the men of Russian nationality the genotype G/G is associated with the early onset of a chronic alcoholization and acute alcoholic psychosis development; (3) for the men older than 35 years of Russian and Tartar nationalities with genotypes carrying an allele G the relative risk of the given pathology is estimated as 5.81.