The aforementioned epidemiological studies have played a central role in defining the importance of plasma lipoprotein disorders in the pathogenesis of atherosclerosis. More specifically, they have been instrumental in establishing plasma lipid and lipoprotein levels such as the plasma concentration of triglyceride, LDL, HDL, and Lp(a), as indicators of CAD risk. The challenge for future epidemiological studies will be to better define the link between CAD and a) the level of particular lipoprotein subfractions, b) factors affecting lipoprotein metabolism, and c) factors affecting the atherogenicity of plasma lipoproteins. For example, it is important to define which triglyceride-rich lipoprotein subfractions are most strongly associated with risk of CAD (e.g., intestinal vs hepatic TRL, large TRL vs smaller TRL remnants) or which subfractions of HDL are most protective (e.g., large vs small HDL, apoE-containing HDL vs apoAI- and All-containing HDL). The relationship between CAD and plasma levels of lipoprotein enzymes and co-factors (e.g., cholesterol ester transfer protein, LCAT), and also compounds that can potentially affect the oxidizability of lipoproteins (e.g., vitamins, paraoxanase) needs to be more clearly defined. Finally, future studies will need to focus not just on the relationship between plasma lipid disorders and atherosclerosis, but between plasma lipids and plaque stability and risk of thrombosis.