Lyme disease is the most common tick-borne illness in the USA and Europe. Pathogens involved include Borrelia burgdorferi in the USA and B. afzelii and B. garinii in Europe. The characteristic rash of erythema migrans occurs in 70 –80% of patients. Neurological disease, including facial palsy, meningo-encephalitis, aseptic meningitis and polyradiculopathy, occurs in 10–15%. Cardiac disease, primarily manifest as heart block, is seen in 1–4%. Arthritis is a late complication in about 30% of untreated patients.