Background: The level of incidence of Tick-borne disease in Latvia still is one of the highest in Europe. There are some similarities between the viral agents, and HLA molecules, because in organism develops one way or another immune response to infection. Clarifying the polymorphisms of HLA molecules will allow to identify regularities of pathological process and to develop a new approach to treating these diseases. The purpose: Of this study was to determine HLA-DR alleles in two groups Latvian patients: in patients with Lyme borreliosis (LB) and patients with Tick-borne encephalitis (TBE). The study included 38 patients with clinical stage -erythema migrans, 60 patients with TBE and 100 control (healthy) persons.All patients and healthy persons are residents of Latvia. HLA genotyping was performed by PCR with sequence-specific primers. Results: The frequency of HLA-DRB1*17(03) (odds ratio, 4.06; pc=0.003), HLA-DRB1*04 (odds ratio, 3.22; pc=0.162), and HLA-DRB1*13 (odds ratio, 2.37; pc=0.055), were higher in patients with LB. And the HLA-DRB1*10 (odds ratio, 0.16; pc=0.044) was smaller in LB patients and significantly higher in controls. Among TBE patients the HLA-DRB1*04 (11 percent vs. 5 percent; odds ratio, 2.58; pc=0.386) and DRB1*17(03) (10 percent vs. 4 percent; odds ratio, 2.67; pc=0.396) alleles were increased, but the HLA-DRB1*01 (2 percent vs. 6 percent; odds ratio, 0.13; pc=0.240) was lower in patients, these differences were not significant after Bonferroni correction. Conclusions: These data suggest the positive association of HLA-DRB1*17(03) allele with Lyme borreliosis in Latvian patients, and HLA-DRB1*10 allele could be associated with a potential protective effect. Among TBE patients statistically significant associations of HLA-DRB1 not detected.