Prostacyclin (PGI2) has been shown to present myocardial protective effects which could be beneficial during cardiac arrest. We tested this hypothesis in a closed-chest dog model in which electromechanical dissociation (EMD) can be predictably observed after 90 to 120 seconds of ventricular fibrillation without chest compression. Six dogs were pretreated with a PGI2 infusion at a rate of 1 mcg/kg/min and six other dogs served as control animals. After 60 seconds of ventricular fibrillation, EMD was already observed in 3 PGI2-treated dogs but in no control dog. After 90 seconds of ventricular fibrillation, EMD was present in 2 PGI2-treated dogs and in 2 control dogs, so that 4 control but only one PGI2-treated animal survived after 90 seconds of ventricular fibrillation. Ventricular defibrillation was also not facilitated in PGI2-treated dogs. The present study does not support PGI2 administration in cardiopulmonary resuscitation.