Secondary prevention studies have shown that lipid-lowering therapy improve angiographic outcome and reduce mortality and incidence of ischemic clinical events in patients with coronary artery disease. The mechanism responsible for the improvement in prognosis seem to be subtle as this improvement cannot be explained by changes in the angiographic diameter of coronary arteries. Atherosclerotic plaque rupture and subsequent thrombosis are the central features in the pathogenesis of acute coronary events: unstable angina, myocardial infarction and sudden death. Cholesterol lowering might decrease the risk of plaque rupture and its thrombogenicity, as well as normalise the impaired endothelial function in hypercholesterolemic patients. In this report, the effects of lipid-lowering therapy on angiographic outcome and incidence of clinical events, in patients suffering from coronary artery disease, are reviewed, and the mechanisms that might explain these findings are discussed.