Inflammation plays a key role in the initiation and progression of atherosclerosis but also in the pathophysiology of atheromatous plaque disruption and the development of acute coronary syndromes. Neopterin is a marker of inflammation and of immune system activation, it is synthesized by macrophages, that, once activated, release this substance. Indeed, in clinical evaluation of patients, measurements of plasma levels of neopterin are usually used to evaluate progression of viral infections, renal transplant rejection, severe systemic inflammatory diseases, nephritic syndrome and several autoimmune diseases. This mediator is able to induce a pro-atherothrombotic phenotype in cells of the coronary circulation. Recent data indicate that serum levels of neopterin are elevated in patients with coronary and peripheral artery disease and seem to be a prognostic marker for major adverse cardiovascular events. In particular, neopterin levels predict future major cardiac and vascular adverse events in patients presenting with chronic coronary artery disease, with acute coronary syndromes, and in those with critical limb ischemia. This renders this molecule a useful marker of atherosclerotic plaque activity, permitting the identification of the subjects at highest risk for major adverse cardiovascular events. In line with the above mentioned evidences, patients with high neopterin levels may require aggressive risk factor modification and intensive medical treatment irrespective of the severity of their coronary artery disease. This data suggest a potential clinical use of neopterin as a marker for disease activity in patients with cardiovascular disease.