The aim of this study was to evaluate the effect of organ oil on isolated heart function before and after ischemia and on the activity of cardiac antioxidant enzymes. 16 Wistar rats were divided into 2 groups; control group and treated group receiving 5 mL/kg/day of organ oil. After 8 weeks of treatment, hearts were perfused and subjected to a global ischemia followed by reperfusion. Activity of cardiac antioxidant enzymes was assessed in freeze-clamped hearts at the end of reperfusion. Results showed that organ oil induces: 1--damage to heart function during the preischemic period, 2--decreased functional recovery during reperfusion and 3--significant increase in catalase activity. It seems that, in our experimental conditions, organ oil increases heart sensitivity to ischemia and reperfusion. However, the mechanism involved has yet to be understood.