The description of Lyme disease in 1976 and the detection of its causative agent, the spirochete Borrelia burgdorferi (B. burgdorferi), in 1982 led to an increase in our knowledge of the course of B. burgdorferi infection and its clinical manifestations. The classic tick-borne dermatoses erythema chronicum migrans (ECM), lymphadenosis benigna cutis (LABC) and acrodermatitis chronica atrophicans (ACA) were proven by isolation of the spirochete from skin lesions to be caused by B. burgdorferi infection. In early disease (less than 1 year) ECM and LABC can develop locally at the site of infection (stage I), but both these skin manifestations can also occur together with multiple lesions after dissemination of the causative organism (stage II). ACA is typical for late infection (greater than 1 year, stage III). High titres of B. burgdorferi antibodies have been found in patients with localized sclerodermalike lesions (circumscribed scleroderma, lichen sclerosus et atrophicus, anetoderma), and frequent simultaneous occurrence of ACA suggests an association with late B. burgdorferi infection. Similarly, we found four cases of cutaneous B-cell lymphoma possibly arising from LABC in association with the same markers of late B. burgdorferi infection. Additionally, some cases of Schönlein-Henoch purpura and of Shulman syndrome may be associated with Lyme borreliosis. The disease is endemic in central Europe, and almost exclusively ticks of the Ixodes ricinus complex seem to transmit B. burgdorferi to humans, whereas the reservoir of infection seem to be rodents, especially mice. The main diagnostic tool is serological examination for B. burgdorferi antibodies, which will become detectable 3-6 weeks after infection. Enzyme-linked immunosorbent assay (ELISA) and the indirect immunofluorescence test (IFT) revealed similar sensitivity. In early disease, sensitivity for antibody detection could be improved by immunoblot technique and by flagellum-ELISA, which is specific for this early sensitizing B. burgdorferi antigen. For treatments, penicillin is no longer recommended as the drug of first choice, because low sensitivity of B. burgdorferi has been observed in vitro and in vivo. Tetracycline, doxycycline and amoxicillin p.o. are now preferred for the treatment of Lyme borreliosis, and in neurologic and cardiac abnormalities ceftriaxone i.v. is recommended. Treatment duration should be 14 days in early disease and 30 days in late disease.