Nitric oxide (NO) is produced by many cells in the body; however, its production by vascular endothelium is particularly important in the regulation of blood flow. Vascular actions of NO include the following: direct vasodilation, indirect vasodilation by inhibiting the vasoconstrictor influences, anti-thrombotic, anti-inflammatory and anti-proliferative effects. Due to its importance in vascular function, abnormal production of NO, occurring in different diseases can adversely affect blood flow and other vascular functions. It has been suggested that alterations in NO generation are a critical cause of injury in the ischemic heart. A biologic link between the endothelial damage and atherosclerotic coronary arterial disease has been presumably related to de - creased arterial bioavailability of NO through the increased leucocyte and platelet adhesions, vasoconstriction and smooth muscle cell proliferation. However, the precise me - chanism of the impaired NO generation is not known, and there is a considerable controversy regarding whether myo - cardial ischemia results in increased or decreased NO for - mation. Asymmetric dimethylarginine (ADMA) is a natural, com petitive inhibitor, and one of the primary factors controlling the nitric oxide production. ADMA was found to be elevated and closely correlated with the impaired vasodilator function in conditions associated with the endothelial dysfunction, such as hypercholesterolemia, hypertension, insulin resistance and type 2 diabetes, and renal failure. But ADMA also seems to be involved in myocardial ischemia, since its plasma levels predict future coronary events in patients with the elevated cardiovascular risk. It has been recently reported that the elevated plasma ADMA concentrations in the acute coronary events are an independent cardiovascular risk factor.