The automatic implantable cardioverter-defibrillator has been implanted in 276 patients with ventricular tachyarrhythmias refractory to therapy with a follow-up period up to 50 months (average 9.75 months). The functional performance of the device has so far been most encouraging. The risks and complications associated with its use are acceptable and quite similar to those observed in patients with implanted pacemakers. Acceleration of ventricular tachycardia to a faster rhythm or to ventricular fibrillation is dealt with successfully through recycling. Actuarial analysis indicates that the device has a significant impact on the survival rate of the implantees, reducing the one-year mortality rate attributed to arrhythmias to only 2%.