CLINICAL PERSPECTIVE: Ventricular fibrillation is a major, but little understood, cause of death. Although defibrillation with electric shock has been in use for several decades, and although many advances have been made in the design of defibrillators (including the development of implantable devices for high-risk patients), this procedure has generally been an empiric one. The mechanisms of the procedures are being intensely studied at Duke University and other institutions in the hope of developing more energy efficient and clinically effective defibrillation equipment.