Lipoprotein (a) (Lp(a)) is a LDL-like lipoprotein with an additional highly polymorphic glycoprotein--apolipoprotein (a) (apo(a)). Apo(a) bears great homology with plasminogen. Lp(a) is synthesized by liver and its degradation may be carried out by a nonspecific process. Apo(a) isoform size and plasma Lp(a) levels are mainly determined by apo(a) gene. Lp(a) can easily be deposited in arterial wall. It promotes growth of smooth muscle cells and inhibits fibrinolysis. These could be the mechanisms by which Lp(a) accelerates atherosclerosis and thrombosis. The physiological role of Lp(a) has not been clearly understood.