['Implantable cardioverter-defibrillator system efficacy is tested at implant by induction of ventricular fibrillation (VF). Defibrillation safety margin can be assessed without VF induction using upper limit of vulnerability methods, but these methods have required manual determination of T-wave timing.', 'To test the feasibility of an inductionless system of implant testing, a multicenter prospective study of an automated vulnerability safety margin system was conducted, which measured T-wave timing using an intracardiac electrogram during a ventricular pacing train. The system delivered up to 4 T-wave shocks of 18 J. Lack of VF induction by all 4 shocks was considered evidence of defibrillation adequacy. Patients subsequently underwent conventional defibrillation testing to meet a standard implant criterion. The 95% lower CI for defibrillation success at 25 J for noninduced patients was found using Bayesian statistics. Sixty patients were enrolled at 6 centers. Vulnerability testing and defibrillation success results were obtained from 54 patients. Vulnerability testing induced VF in 10 (19%) patients, of whom 2 required system revision. All patients not induced by vulnerability testing were successfully defibrillated twice at ≤25 J. The Bayesian credible interval was 97% to 100% for the population success rate of defibrillation at 25 J for automated vulnerability safety margin noninduced patients.'] Does automated vulnerability testing identify patients with inadequate defibrillation safety margin?