Ranolazine, a newer anti-ischemic agent that appears to induce a more efficient utilization of adenosine triphosphate at the cellular level, has been shown to be clinically beneficial in patients with chronic stable angina. More recently, the antiarrhythmic effects of the drug have been described in patients with acute coronary syndromes, as well as in those with atrial fibrillation, when combined with other agents. Experimentally, the predominant inhibitory effects on late I(Na), I(Ca), I(Na-Ca), and I(Ks), with little or no effect on I(to) or I(K1), have been demonstrated. Different experimental models have shown the potential beneficial effect of the drug in both supraventricular and ventricular arrhythmias. Interestingly, despite its potential prolongation of the QT interval, ranolazine does not appear to induce ventricular arrhythmias in animal models. Whether the antiarrhythmic effect is secondary to a more efficient energy production by the cardiac cell or by its direct effect on ion channels is still unclear. The effect of ranolazine on other ionic currents, as well as its potential as a clinically relevant antiarrhythmic agent, still needs to be studied.