The short QT syndrome is a recently described genetic arrhythmogenic disorder, characterized by abnormally short QT intervals and a high incidence of sudden death and atrial fibrillation. Clinical manifestations may also be present in infants; a family history of cardiac sudden death is often present. Gain-of-function mutations in 3 genes encoding potassium channels and loss-of-function mutations in 2 genes encoding the cardiac L-type calcium channel have been identified. Today, the first choice therapy is implantable cardioverter-defibrillator implantation; however, pharmacologic treatment with hydroquinidine, which prolongs QT and reduces the inducibility of ventricular arrhythmias, may be proposed for children and probably for elderly asymptomatic patients.