A correlation exists between circulating levels of low-density lipoprotein cholesterol (LDL-C) and risk of cardiovascular disease (CVD). Evidence from clinical trials indicates that reducing LDL-C levels can result in beneficial clinical outcomes in patients at risk of CVD and in high-risk patients with clinical symptoms of CVD. Lipid-lowering agents, of which HMG-CoA reductase inhibitors (statins) are the most effective, protect against the vascular changes seen in the development of atherosclerotic plaque formation. Clinical trials assessing the effects of statins on coronary atherosclerosis using quantitative coronary angiography or intravascular ultrasound showed that statins can reduce progression or even cause regression of atherosclerotic plaque. This improvement of vascular structure after statin treatment is correlated with reductions in LDL-C levels. This appears to be the principal mechanism by which statin therapy reduces cardiovascular risk, with emerging evidence for statin-mediated changes in high-density lipoprotein and C-reactive protein levels contributing to modification of the atherosclerotic plaque.