Heart rate variability (HRV) is a beat-to-beat variation in cardiac cycle length resulting from autonomic influence on the sinus node of patients in sinus rhythm. The importance of HRV as a risk stratifier has been well accepted, particularly in survivors of myocardial infarction. Large clinical trials are still needed to clarify the role of HRV in patients with non-ischemic cardiomyopathy. Given the significant association between HRV and the development of fatal arrhythmias/sudden cardiac death, HRV has been used in some clinical trials as one of the screening tests to select optimal candidates for implantable cardioverter-defibrillator placement, although its role in this area has not been fully established. Additional large prospective clinical trials are needed to further clarify the predictive value of existing or novel HRV parameters, on their own or in combination with other risk stratifiers, for assessing the risk of sudden cardiac death in a variety of clinical settings.