Introduction: Lipoprotein physiology is the study of fat transport through the aqueous environment of the body. Fats serve primarily two functions in the body. First, phospholipids and cholesterol are the major structural components of all cell membranes. Second, triglycerides and free fatty acids are the major energy sources of the body. It appears that the preferred direction of transport is: (1) for triglycerides to be transported from the gut and liver (where they are absorbed or manufactured) to the muscle (where they are utilized for energy) and fat tissue (where they are stored); and (2) for cholesterol to be transported from all the other tissues back to the liver. It should be remembered that even though no tissue in the body can degrade cholesterol, essentially all tissues make enough cholesterol to be self-sufficient. Therefore, the major problem that most tissues face is an excess of cholesterol, not a deficiency. In fact, it is difficult to find a unique physiological function for LDL. It appears to be the end-product of VLDL metabolism, which must be removed from the plasma before it causes any serious damage to the only tissue with which it has intimate contact, the vascular wall.