Myocardial infarction (MI) was produced in rats with 85, 200 and 300 mg/kg of isoproterenol (ISO) administered subcutaneously (sc) twice at an interval of 24 h. Shift in antioxidant parameters, lactate dehydrogenase (LDH) together with morphological and histopathological changes were investigated. Two hundred mg/kg ISO dose was selected for the present study as this dose offered significant alteration in biochemical parameters along with moderate necrosis in heart. Effect of pre- and co-treatment of hydroalcoholic extract of Ocimum sanctum (Os) at different doses (25, 50, 75, 100, 200 and 400 mg/kg) was investigated against ISO (200 mg/kg) induced myocardial infarction in rats. Modulation of various biochemical parameters and membrane integrity was studied. Os at the dose of 25, 50, 75 and 100 mg/kg reduced significantly glutathione (GSH), superoxide dismutase (SOD) and LDH levels. It also inhibited the lipid peroxidation as observed by the reduced thiobarbituric acid reactive substances (TBARS) levels. In the present study Os at the dose of 50 mg/kg was found to demonstrate maximum cardioprotective effect. Above results were further confirmed by histopathological findings. Thus from the present study it is concluded that Os may be of therapeutic and prophylactic value in the treatment of MI.