In the framework of the ecogenetic research programme, the data are presented on the genetic polymorphism of the vitamin D-binding protein (Gc) in various USSR populations. Blood serum samples were studied, taken from the Russians of the town Yegorievsk, Moscow Region (p = 321) and 113 Russian patients with tuberculosis using the method of isoelectrofocusing. The information was obtained of the Gc frequencies in two population units of Buryats of Aginsky and Ost-Ordynsky Autonomous Districts of Chita and Irkutsk Regions, including the Olkhon island (on the lake Baikal), in totality, 593 individuals and 13 local groups. The position of the studied Russian and Buryat groups within the gene frequency co-ordinate space is well in line with the estimated area of their localization, with regard to the world distribution. Among the Buryat populations studied, there is distinct heterogeneity for which the factor Gc1F plays a leading role within the Gc system/responsible for 92% of all possible genetic variability. Gc factor frequencies in Buryats range within the following limits: 1F.-0.3864-0.6023, 1S-0.1895-0.4535, 2-0.1364-0.2581. For the Russians of Yegorievsk and the patients with tuberculosis of Moscow and Moscow Region following allele frequencies are established: 1-F0.1169, 1S-0.5476, 2-0.1364 and 1F-0.1106, 1S-0.5531, 2-0.3363, respectively, which indicates that no association exists between Gc variants and tuberculosis. The correlation of the Gc allele frequency distribution with the ratio of insulin-independent diabetes (type 2) world-wide indicates that expression of high frequency of diseases is accompanied with comparatively rare characteristic combination of frequencies of three Gc alleles.