Invasive and noninvasive arterial imaging are important techniques used to study atherosclerosis and, specifically, to evaluate the atherogenecity of triglyceride-rich lipoproteins (TRL). Serial coronary angiography trials show significant benefit from lowering low-density lipoprotein cholesterol (LDL-C) which serves to retard lesion progression. Even with aggressive LDL-C reduction, however, up to half of patients demonstrate continued progression of atherosclerosis. Angiographic studies reveal that lowering LDL-C has the most impact on severe lesions, those > or = 50% diameter stenosis, whereas TRL (and their apolipoprotein markers) have been identified as a driving factor behind progression of mild-to-moderate lesions < 50% diameter stenosis. Quantitative coronary angiography (QCA) has demonstrated that progression of mild-to-moderate lesions are among the most significant predictors of clinical coronary events, and that lowering TRL reduces progression of coronary artery disease to the same degree as the lowering of LDL-C.