Brief episodes of myocardial ischemia-reperfusion were shown to be protective against reperfusion injury when used during early reperfusion after a prolonged ischemic episode. This phenomenon has been termed myocardial ischemic postconditioning. In this study, an effect of ischemic postconditioning on persistent reperfusion-induced ventricular fibrillation was studied in the rat isolated heart. 2 minutes of global ischemia on the 15th minute of reperfusion after 30 minutes of regional ischemia effectively abolished the persistent ventricular fibrillation. In non-postconditioned hearts, the ventricular fibrillation continued to the end of reperfusion. The ischemic postconditioning seems to exert a strong antiarrhythmic effect protecting the heart against persistent reperfusion-induced ventricular tachyarrhythmias.