The implantable cardioverter defibrillator is currently a therapy of first choice in patients with malignant therapy refractory ventricular arrhythmias. The occurrence of malignant ventricular tachycardia cannot be suppressed by the defibrillator but is treated using antitachycardia pacing, cardioversion or defibrillation. During recent years, electrodes, defibrillation shockforms and device size were continuously optimized. The development of transvenous lead systems resulted in significant reduction of perioperative mortality and morbidity. With the availability of biphasic shockforms and single-lead unipolar devices marked reduction of defibrillation thresholds were achieved and transvenous lead systems without subcutaneous could be implanted. Improvements in device technology lead to smaller devices which can be implanted subpectorally even using local anaesthesia. But there is still enormous potential to develop an ideal antiarrhythmic device. One of the most significant problems of the defibrillator therapy represents the delivery of inappropriate shocks due to supraventricular tachyarrhythmias and sinustachycardia. To solve this problem different approaches are currently developed. Extension in memory allows to store several data logs and intracardiac electrograms for individual adapted adjustment of the therapy. Intracardiac electrogram width measurement for discrimination between ventricular and supraventricular arrhythmias is currently evaluated. Dual-chamber arrhythmia discrimination algorithms of an integrated dual-chamber pacemaker and defibrillator are clinically studied. Hemodynamic sensors for determining the severity of the arrhythmia are currently under experimental evaluation. The combination of latissimus dorsi dynamic cardiomyoplasty and ICD therapy may improve survival in patients with severely depressed left ventricular function and malignant ventricular arrhythmias. Several randomized prospective trials are currently in progress potentially expanding the use of the ICD in patients at risk for sudden cardiac death. The high costs of defibrillator therapy is still a limitation for its use, but higher production figures and advancing technology could reduce the system prize.