While it is assumed that the normal heart does not predispose to serious arrhythmias, several conditions are now being recognized as being associated with short-lasting ventricular arrhythmias. It also becomes clear that idiopathic VT (or repetitive monomorphic VT) sometimes exists on the background of a compromised heart. Whether this dysfunction is due to the arrhythmia or vice versa is not evident. Finally, VF occurs in patients who, at a first glance, have no apparent heart disease, and it is then called idiopathic VF. These complex electrical abnormalities probably reflect disorders, which often are genetically determined. Recognition of these syndromes, often characterized by abnormal repolarization or a disturbed autonomic function is possible if appropriate techniques are used.