Analysis of long-term data on the infection rated of the taxonomic complex Borrelia burgdorferi s. l. in Ixodes persulcatus and I. ricinus from Moscow Region is carried out. More than 14 000 tick specimens were examined by dark-field microscopy and 704 specimens were investigated by PCR. Two borrelia genospicies, B. afzelii (6.3%) and B. garinii (20%) proved the most prevalent. The genospecies could form a mixtinfection (11%). Borrelia miyamotoi, B. valaisiana, and B. burgdorferi s. s. were also found in the studied territory, with the total ratio lesser than 6%. Acarotropism of Borrelia proved 2.4 times higher with respect to I. persulcatus, than to I. ricinus. Average long-term infection rates of these tick species were 27.3 and 11.3% respectively. Spatial variability of the infection rate in ticks significantly exceeds interannual fluctuations with the variation coefficients 66 and 26% respectively.