The duration of repolarisation is the main determinant of the refractory period and therefore plays a major electrophysiological role. Ventricular repolarisation can be influenced or modified by very many extrinsic factors responsible for so-called secondary changes or anomalies. On the contrary, primary anomalies of ventricular repolarisation correspond to intrinsic anomalies of ionic conduction which in turn affect repolarisation. Primary anomalies of ventricular repolarisation are the consequences of vascular disease, which is the origin of both electrocardiographic anomalies and rhythm disorders, and which can result in sudden death from ventricular fibrillation. Three clinical syndromes correspond with these definitions: long QT syndrome, short QT syndrome, and Brugada syndrome. Much of the experimental work seems to show that arrhythmogenic action results mostly from an increase in the heterogeneity of the refractory periods, whether this involves a prolonged, short or even normal repolarisation time. The various experimental models also give a better understanding of the repolarisation changes observed on the electrocardiogram. Knowledge of the mechanisms responsible for arrhythmias due to primary anomalies of ventricular repolarisation could provide a model for secondary anomalies.