This study was aimed to evaluate the preventive role of S-allylcysteine (SAC) on creatine kinase-MB, iron, iron binding capacity, uric acid, total protein, membrane-bound enzymes such as sodium potassium-dependent adenosine triphosphatase, calcium-dependent adenosine triphosphatase and magnesium-dependent adenosine triphosphatase, and glycoproteins such as hexose, hexosamine, fucose and sialic acid in isoproterenol-induced myocardial infarction in rats. Male albino Wistar rats were pre-treated with SAC (50, 100 and 150 mg/kg) daily for a period of 45 days. After the treatment period, isoproterenol (150 mg/kg) was subcutaneously injected in rats at an interval of 24 hr for 2 days. Isoproterenol-induced rats showed significantly (P < 0.05) increased activities of serum creatine kinase-MB and calcium-dependent adenosine triphosphatase and magnesium-dependent adenosine triphosphatase in the heart, and the levels of iron and uric acid in serum and significantly (P < 0.05) decreased the levels of plasma iron binding capacity, plasma total protein, plasma albumin/globulin ratio and activity of sodium potassium-dependent adenosine triphosphatase in the heart. Isoproterenol induction also showed a significant increase in the levels of glycoproteins in serum and the heart. Pre-treatment with SAC (100 and 150 mg/kg) daily for a period of 45 days exhibited significant (P < 0.05) effect and altered these biochemical parameters positively. SAC (50, 100 and 150 mg/kg) treatment to normal rats did not exhibit any significant effect in any of the parameters studied. Thus, our study shows that SAC has a protective role in isoproterenol-induced myocardial infarction in rats. The observed effects might be due to the free radical scavenging, antioxidant and membrane stabilizing properties of SAC.