The American Heart Association currently recommends the precordial thump as the initial maneuver in the treatment of ventricular tachycardia and monitored ventricular fibrillation. Advocates of the precordial thump maintain that it affords the advantage of immediate availability and might prove lifesaving in cases of ventricular tachycardia. A canine study and a prehospital study have argued that in the cardiac arrest model, thumping ventricular tachycardia causes ventricular fibrillation as often as reversion to a sinus rhythm. We therefore studied the effects of the precordial thump on patients undergoing electrophysiology studies who had been paced into ventricular tachycardia. A total of nine patients received precordial thumps for 11 separate episodes of electrically induced sustained ventricular tachycardia. Our thumps failed on all 11 attempts to convert any of our patients. All 11 were subsequently successfully restored to a supraventricular rhythm with overdrive pacing or countershock. There was no detrimental effect from thumping ventricular tachycardia as has been previously reported. Our results would indicate that countershock is more effective than precordial thumping for converting ventricular tachycardia to a supraventricular rhythm, but previously reported "detrimental effects" of thumping are not confirmed by this study.