Underlying causes of ventricular tachycardia (VT) or complex ventricular arrhythmias (VA) should be treated if possible. Antiarrhythmic drugs should not be used to treat asymptomatic persons with complex VA and no heart disease. Beta blockers are the only antiarrhythmic drugs that have been demonstrated to reduce mortality in patients with VT or complex VA. Radiofrequency catheter ablation of VT has been beneficial in treating selected patients with arrhythmogenic foci of monomorphic VT. The automatic implantable cardioverter-defibrillator (AICD) is the most effective therapy for patients with life-threatening VT or ventricular fibrillation. The American College of Cardiology/American Heart Association Class I indications for an AICD are discussed. Other indications for an AICD are discussed. Patients with AICDs should be treated with biventricular pacing, not with dual-chamber rate-responsive pacing at a rate of 70/minute.