Lyme borreliosis is a tick-borne infectious disease caused by the spirochaetes Borrelia burgdorferi, B. garinii and B. afzelii. It comprises a wide spectrum of symptoms affecting skin, musculoskeletal system, heart, eyes, central and peripheral nervous system. The diagnosis is based on clinical findings in combination with detection of specific IgM and/or IgG antibodies. Diagnostic problems arise from patients with non-specific symptoms and positive IgG antibody detection. Adequate antibiotic therapy cures more than 90% of the patients. However, in some patients repeated therapy is necessary and a small number of patients develop chronic arthritis or other features. While there is currently no vaccine available, prevention of tick bite is the most effective prophylaxis.