Nowadays the standard care for patients at high risk of sudden cardiac death (SCD) or life-threatening ventricular arrhythmias is the implantable cardioverter-defibrillator (ICD) and its variants (S-ICD, CRT-D). Although in the past ICD implantation was associated with routine defibrillation threshold (DFT) testing, recently more and more centers worldwide are abandoning DFT testing, considering the balance between the clinical benefit and increased procedural risks. In spite of this new approach, the usefulness/ suitability of DFT testing – the “to test or not to test” debate – still remains a matter of intense dispute among cardiologists. We present a brief history of ICDs and DFT testing along with the results of key/compelling studies on DFT testing and the management of patients with a high defibrillation threshold.