Abstract <p>A comparative analysis of the quantitative composition of phospholipids and fatty acids of blood erythrocyte membranes and their dimensional characteristics and hemolytic resistance to hemolysis in indigenous and nonindigenous populations of the North of the Russian Federation was carried out. The data on ethnic peculiarities of metabolic reactions in representatives of two ethnic groups (the indigenous population of Mongoloids and the nonindigenous population of Caucasians) were obtained. A notable alteration in the ratio of phospholipid fractions within the erythrocyte membrane was observed in the indigenous Chukchi population. This involved a decline in phosphatidylcholine and its replacement by sphingomyelin and an increase in the values of phosphatidylethanolamine and metabolically active fractions, including phosphatidylserine, phosphatidylinositol, and phosphatidic acid. These findings contrast with those observed in the newly arrived population. Additionally, notable discrepancies were observed in the fatty acid profiles of erythrocyte membrane lipids. The predominant presence of n-3 polyunsaturated fatty acids in the overall lipid composition and in the primary structural phospholipids, namely phosphatidylcholine (PC) and phosphatidylethanolamine (PE), substantiates the ethnic distinctions observed in both indigenous and immigrant populations. These differences in the composition of polyunsaturated fatty acids in the structures of PC and PE indicate the emergence of modified molecular species of these fractions in the indigenous population. The aforementioned ethnic peculiarities in the phospholipid component of erythrocyte membranes result in differences in the dimensional characteristics of erythrocytes and an increase in the resistance of cells to hemolysis in individuals of the indigenous population. In the authors’ opinion, this is not evidence of any deviation from the norm but is more likely to be associated with one of the variants of human metabolism.</p>