Implantable cardioverter defibrillators (ICDs) are being implanted in increasing numbers. At intraoperative defibrillation threshold tests refractory ventricular fibrillation (VF) requiring emergency open chest resuscitation is a major concern during implantation of nonthoracotomy ICD lead systems. A new method of high energy endocardial/extrathoracic defibrillation via the implanted ICD transvenous defibrillation electrode (TDE) was used to terminate refractory VF. During implantation of ICD with TDE in 20 patients refractory VF occurred in two patients. The arrhythmia was terminated with endocardial/extrathoracic defibrillation in both cases, and no complications were observed.