Ventricular tachycardias (VT), shocks, and clusters of shock are ominous signs in patients with implantable cardioverter-defibrillators and herald an increased risk of hospitalization and mortality. VT clusters have been associated with aggravation of heart failure (19%), acute coronary events (14%), and electrolyte imbalance (10%). Yet, any association of potential causative factors and aggravation of VT is vague. Maybe, in patients with any substrate for re-entry, progressive aggravation of ventricular dysrhythmias is to be expected. The high recurrence rate of electrical storm despite antiarrhythmic drug therapy supports this view. The optimal timing of VT ablation is unknown, but current convention is to perform VT ablation after shock clusters or incessant VT has occurred. Preemptive VT ablation before VT has occurred is rarely performed (only in 15% of active centers) and the majority of centers never perform VT ablation even after the first shock. Such practice is within guidelines that recommend VT ablation only in ICD patients with recurrent or incessant VT. However, there is strong data in support of preemptive VT ablation.