The electrocardiogram should be recorded at the very beginning of infectious endocarditis. It provides information on the origin and complications of possible organic disease (aortal stenosis--left ventricular hypertrophy). Moreover regular follow up of ECG tracings can reveal changes signalizing spread of the infection beyond the endocardium. Thus the conduction system may be affected--bundle branch block, atrioventricular blocks grade I to III, ectopic functional tachycardia, extrasystoles, myocardium--by development of typical ECG changes during myocardial infarction after embolization of the vegetation into the coronary artery, or last not least, the pericardium, after spread of the infection into the pericardial cavity with the serious finding of purulent pericarditis with diffuse ST-T elevations on the ECG tracing.