Wistar albino rats (150-200 g) were fed raw garlic homogenate orally in three different doses (125, 250, 500 mg/kg/day) for 30 days. Isoproterenol (85 mg/kg, s.c. 2 doses at 24-h interval, animals sacrificed after 24 h of last injection) induced myocardial necrosis in control rats and after 30 days of garlic feeding. Myocardial oxidative stress was evident following isoproterenol administration by reduction in myocardial superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities along with a rise in plasma thiobarbituric acid reactive substances (TBARS). Myocardial necrosis was evident from the light microscopic and ultrastructural changes, along with a rise in plasma lactate dehydrogenase (LDH). Significant preservation of myocardial SOD activity was observed in all the garlic-fed rats. However, there was no significant change in myocardial reduced glutathione level and GPx activity in any of the treated groups. Significant reduction in plasma TBARS and LDH levels was observed in the 500 mg/kg garlic treated group. Isoproterenol-induced myocardial morphological changes were least in the 250 and 500 mg/kg garlic treated groups. The results suggest that chronic oral administration of raw garlic offered protection against isoproterenol-induced myocardial necrosis and associated oxidative stress.