A forceful blow to the precordium has long been recommended as the first resuscitative measure following cardiac arrest. It has been shown sometimes to cause slowing of ventricular tachycardia. However, reports maintaining that cardiac standstill responded to chest thumping failed to establish the cardiocirculatory conditions at the time of treatment. This study evaluated the maneuver in resuscitating asphyxiated dogs with cardiac standstill, ventricular fibrillation, severe hypotension clinically resembling cardiac arrest, and post-resuscitation tachyarrhythmias.In animals with ventricular tachycardia, precordial thumping caused ventricular fibrillation as often as reversion to sinus rhythm. Used during severe hypotension it had no effect; nor did it precipitate cardiac asystole, ventricular fibrillation or ventricular tachycardia. No animal with cardiac standstill or ventricular fibrillation was benefited by thumping while artificial ventilation, external cardiac massage, intravenous epinephrine and external countershock restored 14 of 15 animals.It would appear that precordial thumping should be utilized in the management of ventricular tachycardia only when equipment for external defibrillation is immediately available. The measure should be deleted from the recommended treatment of cardiac arrest.