The purpose of this study was to assess the relative frequency of the known HLA-B27 subtypes in HLA-B27 positive Chukotka natives, which have higher frequencies of HLA-B27 (to 40%) and spondyloarthropathies (to 2%) than the Russian Caucasian population. Using oligotyping of the polymerase-chain reaction amplified second and third exons of the HLA-B27 gene in 86 DNA samples from HLA-B27 positive individuals were successfully typed. All had HLA-B*2705, including 4 patients with Reiter's syndrome and 5 with ankylosing spondyloarthritis, except one Eskimo who had HLA-B*2702. None had HLA-B*2704, a frequent subtype in Orientals. With respect to HLA-B27 subtypes the indigenous populations from the eastern part of the Chukotka Peninsula are genetically more closely related to Caucasians than to Orientalis.