Atherosclerosis and cardiovascular disease are caused by a complex cascade of events in which low density lipoprotein (LDL) particles play a key role.  Lipoproteins are water soluble transport particles that carry cholesterol and triglyceride throughout the blood stream.  Many complex processes interact with LDL particles decreasing their size and increasing their density. This conversion makes LDL particles more likely to interact with the arterial wall where they can deposit their cholesterol and other lipid contents and initiate atherosclerosis. Knowing the number and type of LDL particles can aid in the diagnosis and management of cardiovascular disease risk.