Hyperlipidemia is first detected by an increase in the plasma concentrations of cholesterol and/or triglycerides, and implies an abnormality of plasma lipoprotein metabolism. Disorders of lipoprotein metabolism are often classified specifically according to the lipoprotein affected. The WHO classification of lipoprotein phenotypes is a useful means of showing which lipoproteins are present in excess in individual hyperlipidemic patients. Hyperlipoproteinemia can be secondary to other well-known diseases that affect plasma lipoprotein metabolism, for example, diabetes mellitus, hypothyroidism or nephrotic syndrome. When such diseases are excluded, the hyperlipoproteinemia is defined as primary hyperlipoproteinemia. Many primary hyperlipoproteinemias have a genetic basis and the underlying molecular defect has been clarified in some genetic disorders. Hyperlipoproteinemia is considered to be one of the major risk factors for atherosclerosis and the development of atherosclerosis depends on the type of hyperlipoproteinemia. In this sense, familial hypercholesterolemia is a clinically important primary hyperlipoproteinemia because of its high risk of ischemic heart disease and its high prevalence in a normal population (1/500). It is necessary to make an exact diagnosis of specific genetic disorder, if possible, to provide prognostic and therapeutic information.