In this review, the up-to-date understanding of the molecular basis of primary ventricular arrhythmias is outlined. Two disorders have recently been well described at the molecular level, the long QT syndromes and Brugada syndrome, and we review the current scientific knowledge of each disease. Two other disorders, arrhythmogenic right ventricular dysplasia and Wolff-Parkinson-White syndrome, which are on the cusp of understanding, are also described.