Ventricular tachyarrhythmias include potentially lethal episodes of sustained ventricular tachycardia (VT) and ventricular fibrillation (VF) as well as hemodynamically tolerated ventricular ectopic activity. Sustained VT or VF may develop in the setting of acute myocardial infarction or as clinical sequelae of advanced cardiomyopathy. The incidence of these serious arrhythmias is estimated from retrospective and observational studies and registries of sudden cardiac arrest and sudden cardiac death. Over the past few decades, there has been a gradual decline in the incidence of life-threatening ventricular tachyarrhythmias which has been largely driven by upstream treatments for and prevention of coronary artery disease and its sequelae. In addition primary prevention implantable cardioverter–defibrillators (ICDs) have improved survival in patients at risk for malignant ventricular arrhythmias and sudden cardiac death. Improved understanding, and improved diagnostic and imaging methods have elucidated many of the previously classified “idiopathic” ventricular arrhythmias as inherited arrhythmic syndromes and occult cardiomyopathies. In addition, improved sensitivity and duration of ECG monitoring has allowed increased detection of ventricular ectopic activity.