The implantable cardioverter-defibrillator (ICD), when implanted in the late phase of myocardial infarction (MI) in the primary prevention of sudden cardiac death, reduces total mortality by 23-31%. Current guidelines recommend ICD implantation at least 40 days after MI. Despite optimal MI therapy, the risk of sudden cardiac death or cardiac arrest remains highest within the first 30 days after index infarction. Two randomized trials with ICD implantation early after MI failed to show the reduction of total mortality in a long-term follow-up study. The decrease of sudden cardiac death incidence was counterbalanced by an increase of nonsudden deaths, which may have been caused by the augmentation of heart failure deaths in ICD groups, presumably due to ICD interventions. Therefore, optimizing ICD appears to be the most important issue influencing the long-term outcome.