Serum blood samples from 796 of the total 1600 Forest Nentsi, the members of the isolate in the north-western part of Siberia were tested for the G1m (z, a, x, f), G2m (n), G3m (g, b0, b1, b3, b5, s, t) and Km (1) antigens. Significant heterogeneity in local Gm haplotype and Km1 allele frequencies has been found. The frequencies of "deleted" Gm (-; n; b) and Gm (-;..; g) haplotypes were found to be equal 0,020 and 0,004, respectively. When segregation disturbances for the Gm locus were inspected in 102 families, no apparent deviations from Mendelian expectations occurred. Blent, Oriental-Caucasian origin of Forest Nentsi has been confirmed by the presence of "Northern Oriental" Gm (za; b035st) and "Caucasian" Gm (f; b0135) markers showing the frequency of 0.199 and 136, respectively.