Ticks, mosquitoes and mosquito larvae from various localities of the Czech Republic were examined for the presence of pathogenic borreliae using PCR method throughout 10 years (1997-2007). We found significantly higher positivity of ticks for borreliae compared to mosquitoes adults and mosquito larvae. We isolated two bacteria strains from Culex (Culex) pipiens s.l., one identified as B. afzelii, one identified as non B.b.s.l. In 2004-2005, arthropods (members of the order Acarina and Siphonaptera) from the hair of the small rodents (Apodemus flavicollis, Clethrionomys glareolus) were collected. The most predominant species was Laelaps agilis. 9 samples from Acarina and 4 from Siphonaptera were found to react positive for B. burgdorferi s.l. DNA by PCR method. Presented results imply certain possibility of borrelian transmission by mosquitoes. Our data show that at least some mite and flea species are able to harbor borreliae.