Genetic markers--blood groups ABO, RH, MN; serum proteins HP, PI, TF, C3; erythrocyte enzymes ACP1, ESD, AK1, PGM1, GLO1, PGD, PGP; and the other: PTC-tasting, ear wax types and color vision, were studied in two aboriginal Buryatian populations of Baikal Lake region: in Chitinskaya and Irkutskaya Provinces. Two samples were further divided into subgroups, according to their health status: "healthy", "indefinite" and "sick" by means of special regression procedure. The "healthy" subgroup of the Chitinskaya Province population is characterized by higher frequencies of PTC-tasters: 0.871 vs. 0.757 in the "sick" part (chi 2 = 5.36, p less than 0.05); higher frequency of the phenotype PI M1M1: 0.734 in "healthy" vs. 0.547 in "sick" (chi 2 = 8.89, p less than 0.01); also, lower frequency of the PI M1M2 phenotype: 0.148 and 0.299, respectively (chi 2 = 7.49, p less than 0.01); the frequencies of the phenotype TF C2C2 are: 0.015 and 0.076 (chi 2 = 5.48, p less than 0.05). In Irkutskaya Province population differences between "healthy" and "sick" subgroups were discovered for blood group AB: "healthy" 0.046 and "sick"--0.175 (chi 2 = 11.28, p less than 0.010); for GC (1F-2)--0.214 and 0.116 (chi 2 = 4.45, p less than 0.05). Some other differences between "healthy" and "sick" in both populations are not significant. Some trends concerning heterozygosity in loci--GC, PGM, TF were discovered. The results are considered from the viewpoint of higher fitness of some genetic traits in the populations studied.