The electrical defibrillator has been proven to be a life-saving device in the treatment of cardiac arrest due to ventricular tachycardia or ventricular fibrillation. An understanding of the physiology and technology behind this device is useful for providers of emergency care. In this article, we review the current concepts in electrical defibrillation and briefly discuss the developmental history. The physiology and the technical considerations will make up the bulk of the discussion. The latest developments in electrical defibrillation also will be reviewed.