The clinical benefit of standard (single-chamber) implantable cardioverter defibrillator (ICD) therapy in elderly patients or in subjects with moderate or severe heart failure who had ventricular tachyarrhythmias has been debated. We studied the follow-up of 450 patients who underwent standard ICD implantation at our institution in relation to the functional status of heart failure (New York Heart Association Class) or patient’s age. During a mean follow-up of 24±28 months (range, <1–114 months), 90 patients (23%) died: 9 patients (2%) from sudden arrhythmic death and 5 patients (1%) suddenly, but probably not from arrhythmic causes; 55 patients (14%) died from congestive heart failure and/or myocardial reinfarction and 21 patients (5%) from noncardiac causes. We could clearly demonstrate that ICD therapy was able to prevent sudden cardiac death, both in patients with severely depressed left ventricular function and in patients aged ≥65 years. An important step forward in ICD technology was the introduction of dual-chamber pacing possibilities to improve left ventricular dysfunction and to allow a more individualized ICD therapy. At our institution, we have implanted a dual-chamber ICD in 15 patients. Preliminary results showed that heart failure improved in 5 patients (33%) and remained unchanged in 10 patients (67%, p = not significant). There were no patients who had a lesser degree of heart failure after implant. Based on our experience so far, in addition to the hemodynamic benefits of dual-chamber ICDs, dual-chamber sensing and waveform storage capabilities are very helpful and promising diagnostic tools for the detection and handling of inappropriate ICD therapies.