Lyme disease is a recognised cause of atrioventricular heart block. In the majority of cases conduction disturbances are reversed with antibiotic treatment. The diagnosis of Lyme disease is not always obvious and its recognition is important if unnecessary implantation of a permanent pacemaker is to be avoided. A 34-year-old man presented to our hospital with complete heart block due to Lyme carditis. This resolved completely within a few days after treatment with appropriate antibiotics.