In order to study the antibody seroprevalence of the causal agent of Lyme borreliosis, <i>Borrelia burgdorferi</i> sensu lato (s.l.), and the history of tick bites at a geographical distribution limit of <i>Ixodes ricinus</i>, we compared healthy blood donors in geographically extreme regions: the borreliosis-endemic Vestfold County (59°N) and the region of northern Norway. Blood samples were screened ...