Sudden cardiac death (SCD) is one of the leading causes of mortality in developing countries. To prevent SCD, it is crucial to have effective tools for identifying patients at risk, given that there are now effective devices and medications that can prevent SCD. Two noninvasive electrocardiographic tools have been approved by the Food and Drug Administration and are being used clinically for identifying patients at risk for SCD: the signal-averaged electrocardiogram (SAECG) and T-wave alternans (TWA). This article reviews each of these approaches and includes a discussion of the mechanisms and a summary of the clinical studies published to date.