The usefulness of the implantable cardioverter defibrillator (ICD) for the prevention of sudden cardiac death caused by ventricular tachyarrhythmias has been proven by several international randomized multi-center clinical trials. Recent advances in medical technologies, such as size reduction and the functional improvements of the device, have resulted in relatively easy implantation. As a result, the number of ICD recipients has been rapidly increasing and the indications for ICD implantation have been expanding. Dual chamber ICDs offer improved tachyarrhythmia detection algorithms such as discrimination of supraventricular arrhythmias. In Europe and the United States, biventricular ICDs are now available for the treatment of congestive heart failure associated with ventricular tachyarrhythmias. Although the incidence of inappropriate shock by ICDs is decreasing, inappropriate discharges of ICDs and a declining quality of life are still problems.