Although the cardiac manifestations of Lyme disease may be diverse, in general they are treatable with currently available therapies. A high index of suspicion is required to make a diagnosis, especially for patients who may lack a suggestive history of tick exposure or residence in an endemic region. Lyme disease-related heart block may require pacemaker insertion and supportive care. The efficacy of antibiotics in the therapy of acute and chronic cardiac Lyme disease will require further study. Serologic testing and cardiac histopathology are the most precise methods of diagnosis. There is a need to develop more sensitive and specific diagnostic tests for Lyme disease and for Lyme carditis in particular.