The term 'ventricular arrhythmias' incorporates a wide spectrum of abnormal cardiac rhythms, from single premature ventricular complexes to sustained monomorphic ventricular tachycardia (VT), polymorphic VT, and ventricular fibrillation. Sustained ventricular arrhythmias are the most common cause of sudden cardiac death. These arrhythmias occur predominantly in patients with structural heart disease, but are also seen in patients with no demonstrable cardiac disease. The diagnosis of VT can be made reliably using electrocardiographic criteria, and a number of algorithms have been proposed. Among patients with VT and a structurally normal heart, the prognosis is usually benign and treatment is predominantly focused on the elimination of symptoms. Patients who have VT in the presence of structural heart disease are often managed with implantable cardioverter-defibrillators. These devices are effective for both primary and secondary prevention of VT and sudden cardiac death. Pharmacological therapy for VT has limited efficacy and is associated with a high incidence of adverse effects. Radiofrequency catheter ablation is useful for controlling recurrent episodes of monomorphic VT; however, research is needed to define the role of catheter ablation in the treatment of other ventricular arrhythmias.