The effects of 3,6-dimethylamino-dibenzopyriodonium edetate (IHC-72) on global ischemia reperfused rat hearts were investigated. In the isolated working rat heart, 40-min global ischemia followed by 30-min reperfusion resulted in increases of ventricular tachycardia (VT) and ventricular fibrillation (VF), increases of creatine kinase (CK) release and malondialdehyde (MDA) contents, but decreased superoxide dismutase (SOD) activity. Following ischemia and reperfusion, the accumulation of myocardial calcium increased. IHC-72 50 mumol.L-1 given 10 min before ischemia and during reperfusion decreased the cardiac CK release, VT, and VF, reduced the MDA contents, prevented the reduction of SOD activity and attenuated the accumulation of myocardial calcium and sodium vs control. These results indicated that IHC-72 protected myocardial reperfused injury.