According to current opinion there is acute, self-limiting Lyme carditis, and chronic Lyme carditis. Acute Lyme carditis manifests mostly as transient conduction disorders of the heart (e.g. AV-blocking I to III), and as supraventricular and ventricular rhythm disturbances, pericarditis, myocarditis, and pancarditis in single cases. Chronic Lyme carditis is defined as a case of chronic heart failure confirmed by positive serology and endomyocardial biopsy. Anamnestic aid is rare. Neither tick-bites nor preceding or accompanying erythema chronicum migrans are constantly reported. Seropositivity and control of its specificity by western blot are indicative but no etiological proof. Even histological detection of spirochetes in endomyocardial tissue or cultivation of borrelia from endomyocardial biopsy are no final etiological proof of the respective cardial disorder. Those findings, however, are an indication for antibiotic treatment. According to the severity of the disorder, antibiotics are administered orally (penicillin or derivatives) or parenterally with penicillin or cephalosporins of the 3rd generation over 4 and 2 weeks, respectively.