We studied the relationship between the GPx-1 gene Pro198Leu polymorphism genotype and activity of free-radical processes. In patients with documented CHD, the content of lipoperoxides and MDA in LDL, activity of glutathione peroxidase in erythrocytes, and genotype of GPx-1 gene Pro198Leu polymorphism were determined. In carriers of the minor allele, activity of glutathione peroxidase in erythrocytes was lower by 17% than in wild allele homozygotes, while the content of lipoperoxides and MDA in LDL was higher by 74 and 27%, respectively. We concluded than free-radical oxidation processes are more pronounced in carriers of the minor allele of GPx-1 gene Pro198Leu polymorphism.