The Ventritex Cadence Model V-100 Tiered Therapy Defibrillator is a third generation antitachyarrhythmia device currently completing clinical trials in the United States. The implantable pulse generator is capable of high energy defibrillation, low energy cardioversion, as well as antitachycardia and bradycardia pacing. In addition, this microprocessor controlled device can deliver monophasic or biphasic defibrillation/cardioversion shocks, is noncommitted to deliver shock therapy after initiating charging for defibrillation or cardioversion therapy, and can store electrograms of spontaneous tachyarrhythmia episodes. These expanded device capabilities should improve therapy efficacy and patient management, and represent a major advance in the treatment of patients with ventricular tachyarrhythmias.