The genetic structure of three Asiatic eskimos subpopulations (402 individuals), five coast chuckchies subpopulations (1793 individuals) and three reindeer chuckchies subpopulations (559 individuals) have been studied for 26 electrophoretic protein systems (33 loci). These are: adenilate-kinase (AK), diaphorase NAD X H (Dia), glyoxalase-1 (GLO-1), glucose-6-phosphate dehydrogenase (6GPT), glutamatpyruvate transaminase (GPT), glutamicoxalate transaminase (GOT), carbonic anhydrase-1 (Ca-1), catalase (Ct), acid phosphatase (AcP), lactate dehydrogenase (loci LDH-A and LDH-B), leucine aminopeptidase (Lap), malatedehydrogenase (MDH), purine nucleoside phosphorylase (PNP), superoxide dismutase (Sod), 6-phosphogluconate dehydrogenase (PGD), phosphoglucomutase (loci PGM1 and PGM2), cholinesterase (loci c1--c5), alkaline phosphatase (Pp), esterase D (EsD), red cell esterase (Est) - 4 loci, albumin (Alb), haptoglobin (Hp), hemoglobine (Hb A and B), group-specific component (Gc), transferrin (Tf), ceruloplasmin (Cp). In addition, AB0 and Rh system blood groups and phenyl thiocarbamide taste sensitivity (PTC) have been studied. 12 of 36 loci are polymorphic (33.33%), heterozygosity for all loci in eskimos, coastal and reindeer chuckchies being 0.118 +/- 0.005, 0.130 +/- 0.002 and 0.120 +/- 0.004, respectively. These estimates do not differ essentially from heterozygosity at these loci for mongoloid groups living further south. The test for interpopulation heterogeneity has permitted to estimate contribution of the loci to the differentiation of these populations. The least heterogeneity has been found at loci where gene frequency distribution is the most specific for these ethnic groups.