Objectives We sought to determine the value of electrophysiology (EP) testing in patients with ventricular fibrillation (VF), ventricular tachycardia (VT) with syncope, or sustained VT in the setting of left ventricular dysfunction. Background Traditionally, EP testing is part of the workup of patients with sustained VT or VF. Recently, some have suggested that EP testing is unnecessary in these patients, many of whom are likely to receive an implantable cardioverter-defibrillator (ICD). Methods Within a multicenter trial (Antiarrhythmics Versus Implantable Defibrillators) designed to evaluate whether drugs or ICD resulted in a better outcome, data were analyzed regarding EP testing. Although this testing was not required, it was performed in >50% of patients. Information regarding the results of EP testing was correlated to baseline clinical characteristics and outcome. Results Of 572 patients subjected to an EP test, 384 (67%) had inducible sustained VT or VF. Inducible patients were more likely to have coronary artery disease, previous infarction, and VT as their index arrhythmic event. Inducibility of VT or VF did not predict death or recurrent VT or VF. Conclusions Information derived from EP testing in this patient population, particularly those with VF, is of limited value and may not be worth the risks and costs of the procedure, particularly in those patients likely to receive an ICD. (Am Heart J 2002;144:478-84.)