In the group of long-livers of the North-West of Russia, I/D polymorphism of angiotensin-converting enzyme (ACE) gene and C102T polymorphism of serotonin receptor (5-HT2A) gene were studied. No reliable differences in allele frequency of these genes between long-livers and young people were detected. Nevertheless, highly pronounced difference in the A1/A2 allele frequency of 5-HT2A gene between populations of the North-West of Russia, on the one hand, and of the USA, on the other hand, was discovered (i.e. 0.397(A1), 0.603(A2), and 0.615(A1), 0.385(A2), respectively). Differences of this kind between the two populations deserve special consideration, conditioning the necessity of further detailed analysis of other genes of the serotonin system in the populations of other regions of Russia.