The survival rate of 2256 patients with pacemakers was analyzed. Patients paced for Adams-Stokes equivalents (e.g. dizziness) showed a significantly better survival rate than did patients with pacemakers implanted for Adam-Stokes attacks or heart failure (P less than 0.0001). The estimated survival of the latter two groups did not differ significantly. Of the deceased patients who had received a pacemaker for the treatment of heart failure, 54% died due to this condition despite pacemaker implantation. The relative percentage of cases of sudden death after pacemaker implantation was high in the groups with Adams-Stokes attacks (12%) and Adams-Stokes equivalents (13%). In patients paced for Adams-Stokes attacks, sudden death occurred more frequently in the first year after pacemaker implantation (P less than 0.015) than during the following years. Therefore, increased efforts should be made to monitor patients carefully after pacemaker implantation to enable prompt detection of malignant tachyarrhythmias, probably the cause of sudden death in a substantial number of patients with pacemakers.