The familial long QT syndrome (LQTS) is now recognized as a genetic channelopathy with a propensity to arrhythmogenic syncope and sudden death. Three genetic mutations have been identified that involve the slow and fast delayed potassium rectifier currents and the sodium current. Distinctive ECG-T wave phenotypes are associated with each of the three genotypes. Current day therapy includes: beta-adrenergic blocking drugs; pacemakers; left cervicothoracic sympathetic ganglionectomy; implanted cardioverter defibrillators; and possibly, drugs that improve mutant ionic channel dysfunction. LQTS has provided unique insight into the complex relationship between ionic channel dysfunction and ventricular tachyarrhythmias.