Abstract: The effects of arginine aspirin (AAs) on the effective refractory period (ERP) and ventricular fibrillation threshold (VFT) of ischemic ventricular muscle were observed in 24 anesthtized openchest rabbits. that the platelet aggregation rate was shown to be increased by 11±5%, and VFT decreased by 24±3 mA at 50 min after coronary occlusion. Compared with values at 10 min postocclusion, ERP of ventricular muscle in border ischemie zone (BIZ) and central ischemic zone (CIZ) was shortened by 20±10% and prolonged by 35±22 ms, respectively, and dispersions of ERP between CIZ and BIZ were increased by 52±17 ms, compared with control values, (p<0.01) By giving an intravenous injection of AAs at 0.5h before coronary occlusion, changes in parameters as mentioned above were obviously relieved as compared with the same paramekers in the group of simple coronary occlusion at 50 min postocclusion, (p<0.01).These results suggest that AAs may inhibit platelet aggregation, reduce dispersions of ERP and elevate VFT after coronary occlusion.