Lyme borreliosis is an infection caused by the Borrelia burgdorferi sensu lato complex and transmitted by Ixodes ricinus ticks in Denmark. It can manifest itself in several different forms of which erythema migrans is the most common and is diagnosed by clinical assessment of the characteristic erythema. Laboratory support for the clinical diagnosis of other manifestations rests on the measurement of Borrelia-specific antibodies. Treatment is straight-forward with antibiotics such as penicillin. This paper reviews the clinical manifestations, diagnosis and treatment of this infection.