Significant advances have been made in the therapy of ventricular arrhythmias. Many new antiarrhythmic drugs have expanded the medical armamentarium to treat ventricular tachycardia and ventricular fibrillation, and the use of intracardiac electrophysiologic studies has aided in predicting long-term drug efficacy. Major advances have also been made in the surgical treatment of arrhythmias. However, there remain a number of patients in whom ventricular arrhythmias remain a major therapeutic problem and, in some of these, electrical devices may aid in treatment. Overdrive pacing may prevent certain cases of ventricular arrhythmias, and antitachycardia devices may be useful in terminating paroxysmal ventricular tachycardia. In certain circumstances, internal cardioversion or defibrillation may be an alternative. At present, antitachycardia pacing and internal countershock must be considered as forms of therapy to be used when medical and surgical therapy are impractical or have failed. Careful selection is necessary to delineate patients in whom these forms of therapy may be indicated.