Management strategies are urgently needed for the problem of sudden cardiac death, the most common single, non-accidental cause of death in adults in North America. Many consider that the problem of sudden cardiac death has reached epidemic proportions. Contemporary prophylactic management of sudden cardiac death includes identification of high risk populations, based on underlying structural heart disease, degree of left ventricular dysfunction, and evidence of a ventricular arrhythmia propensity. Populations with the highest sudden death cardiac risk, notably those patients resuscitated from spontaneous episodes of sustained ventricular tachyarrhythmias, have been used as test populations for the development of effective prophylactic approaches. However, in such populations, ethical considerations have precluded the use of untreated control groups. Furthermore, such patients comprise only a small proportion of the total patient population that could benefit from an effective prophylactic strategy. The largest 'at-risk' group are those patients with coronary artery disease and depressed left ventricular function who have, but have not yet expressed, a ventricular tachyarrhythmia propensity. The major advantages of a controlled trial of prophylactic therapy in the latter population are evaluation of sudden death prophylaxis in the larger 'at-risk' population and the opportunity to do so with an untreated control group. The 'window of opportunity' for such comparisons has been closed in resuscitated patients for some time and is in danger of closing in the larger population. The total absence of controlled efficacy data for ICD use despite 30,000 implanted units of this expensive technology argues strongly for the timely acquisition of controlled data in the larger population before the therapy is embraced any further.