Sudden cardiac arrest is a leading cause of death in industrialized countries. There is solid clinical evidence for implantable cardioverter-defibrillators as the only effective means of preventing sudden cardiac arrest and reducing mortality in high-risk patients. The therapeutic strategy has definitively been validated, but we have not yet identified with the same effectiveness the patients who most likely will benefit from such therapy. Risk stratification of sudden death is therefore one of the major unresolved issues of modern cardiology. Current guidelines identify ejection fraction as the only instrumental parameter for risk stratification of sudden cardiac death. It is strongly consolidated from "old and new" clinical trials that ejection fraction reduction is the real powerful predictor of total mortality and sudden death regardless of its etiology; however it cannot be considered as an indisputable gold standard predictor of risk because it lacks of sensitivity and specificity in the prediction of sudden death. It is reasonable that many factors besides ejection fraction influence patient prognosis; there are different aspects suggesting that a reduction in ejection fraction is a risk factor only in combination with other risk factors. The implantable cardioverter-defibrillator therapy is expensive and associated with possible complications. We therefore need better methods for risk stratification of our patients in order to increase the real cost-effectiveness of current and future treatment options.