Extracellular superoxide dismutase (EC-SOD) is a secretory glycoprotein with an affinity for heparin-like substances.  The plasma EC-SOD level might affect the physiological and pathological conditions of the vascular system, since this SOD isoenzyme is the principal enzymatic scavenger of superoxide (O₂^-) in the extracellular space and is present in the circulation in equilibrium between the plasma phase and the glycosaminoglycans on the endothelium.  There is growing evidence that almost all diseases including lifestyle related diseases are related, more or less, to oxidative stress.  This review will discuss the characteristics of EC-SOD and the role of EC-SOD in some lifestyle related diseases.