Infection with tick-borne spirochetes (e.g. Borrelia burgdorferi) may lead to the development of erythema chronicum migrans, acrodermatitis atrophicans, meningopolyneuritis Bannwarth, and a special type of reactive arthritis named Lyme disease after the American endemic area. Since these diseases occur also in Austria, their clinical features are described in this review; a clear distinction must be made between the neurological manifestation of Lyme disease and those of tick-bite mediated early summer meningoencephalitis. Serological tests can prove that an infection with Borrelia burgdorferi has occurred. The treatment of choice is tetracyclines in the early stages of the disease.