In a number of patients the etiology of syncope remains unexplained despite of diagnostic effort. A significant proportion of unexplainable syncope is arrhythmogenic syncope. Gold standard for the diagnostics of arrhythmogenic syncope is the evidence of arrhythmia at the loss of consciousness during the patient’s monitoring. An implantable loop recorder is a modern modification of the electrocardiographic monitoring system. The benefit of loop recorder implantation in the diagnostics of syncope consists of three aspects: 1. it documents the arrhythmia during its symptoms and in this way it proves the arrhythmic causes of syncope 2. it documents the absence of arrhythmia during syncope and excludes arrhythmic etiology of syncope and 3. it determines the therapeutic strategy.