At approximately 28 clinical sites, patients with ventricular tachycardia or ventricular fibrillation were screened. Those with ventricular fibrillation or serious ventricular tachycardia were entered into a registry for long-term mortality follow-up using the National Death Index. Patients with the prospect of long-term benefit from an ICD and/or antiarrhythmic drug therapy and without exclusions to an ICD or to amiodarone and without a transient or correctible cause of the index event were entered into the trial.