The implantable cardioverter defibrillator (ICD) is an established therapy for improving mortality for primary and secondary prevention of sudden cardiac death. Whether to perform defibrillation threshold testing (DFT) either intraoperatively or post-operatively remains a controversial issue.1-6 The DFT is defined as the minimum energy required at which two shocks can successfully terminate ventricular fibrillation and dates from the era of surgically implanted devices with epicardial patches.7 Typically, a safety margin of at least 10J is employed for device programming, though some trial data suggest that a margin of 5J could be just as effective.8 Various methods have been utilized to perform DFT testing, and no particular method has been shown to be superior to another (Figure 1). Previously, guideline recommendations addressed the indications for ICD implantation but did not comment on DFT testing.9 Recent consensus statements now provide some guidance as to when it is appropriate to perform or not perform DFT testing in light of new trial data.10 This review will address some of the risk factors for having a higher DFT, impact of DFT testing on patient outcomes, and some of the risks and contraindications of DFT testing.