The consumption of diets rich in plant foods is associated with a reduced risk of cardiovascular diseases. This study aimed to evaluate the preventive role of rutin on lipid peroxides and antioxidants in normal and isoproterenol-induced myocardial infarction in rats. Subcutaneous injection of isoproterenol (150 mg kg(-1)) to male Wistar rats at an interval of 24 h for two days showed a significant increase in the activity of serum cardiac marker enzymes (creatine kinase, lactate dehydrogenase, aspartate transaminase and alanine transaminase) and a significant decrease in the activity of these enzymes in the heart. Lipid peroxidative products (thiobarbituricacid reactive substances and lipid hydroperoxides) were significantly increased and enzymic (superoxide dismutase, catalase and glutathione peroxidase) and non-enzymic (reduced glutathione and vitamin C) antioxidants showed a significant decrease in isoproterenol-treated rats. Pretreatment with rutin (40 or 80 mg kg(-1)) to isoproterenol-treated rats orally for a period of 42 days daily caused a significant effect. Administration of rutin to normal rats did not have any significant effect on any of the parameters studied. The results of our study show that rutin possesses antioxidant activity in isoproterenol-induced experimental myocardial infarction.