Several studies have uniformly demonstrated a marked reduction in expected arrhythmic/sudden death rates in patients with either drug-refractory sustained ventricular tachycardia, ventricular fibrillation or survivors of cardiac arrest following the implantation of cardioverter-defibrillators (ICD). Significant advances in these devices over the past 10 years have permitted programmability and demand pacing. There has been sophistication in tachycardia detection and the characteristics of the delivered electrical therapy. Programs to reconfirm the arrhythmic event, sensing parameters for rate, electrogram amplitude, data storage, interrogation and morphology are available in some devices. Some models will permit both antitachycardia pacing as well as defibrillation functions and choice of shock waveforms as bidirectional and biphasic shocks. Endocardial lead systems using smaller and more flexible electrodes may obliterate the need for thoracotomy. It appears that ICD therapy will form a significant component in antiarrhythmic therapy in the future.