The aim of the study was to estimate the prevalence of Borrelia burgdorferi antibodies among healthy population of randomly selected voivodeships in Poland. The presence of antibodies was tested by ELISA. Of 1000 blood samples taken from healthy blood donors, antibodies were detected in 11-13% of samples. The results indicate a contact with infecting agent and a possibility of asymptomatic course of the Lyme borreliosis. Frequencies of B. burgdorferi antibodies in blood donors in spring and in autumn were compared. An increase in the proportion of persons positive for IgM antibodies in September may indicate a seasonal transmission and possibility of Lyme borreliosis acquirement according to the biological activity of ticks.