Lipoprotein(a) [Lp(a)] is a high molecular weight plasma protein structurally related to low density lipoprotein (LDL), but with distinct metabolic and biologic features. Six different isotypes may be found among the general population; they are inherited as a codominant autosomic monogenic trait. Lp(a) levels in the blood are strictly conditioned by the isotype and much less, if at all, by other environmental or metabolic factors. The Lp(a) catabolic rate is very similar among different individuals and comes from the balance of two complementary pathways: uptake from blood by tissue cells via LDL-receptors, and non-receptor macrophagic internalization at the level of the reticulo-endothelial system. Its high content in lysolecithins and cholesterol, and the close structural similarity of its peptidic component to plasminogen, make Lp(a) a crucial "meeting point" of two main physiopathologic elements of atherogenesis:lipoprotein metabolism and fibrinolysis. This particular role would seem to explain the experimental finding of a close relation between Lp(a) plasmatic levels and the severity of atheromatous processes. Deep understanding of Lp(a) physiopathology is therefore expected to be a powerful tool for the creation of a comprehensive and practical model of atherogenesis and to enable us to deal with prognostic, preventive and therapeutic problems in this field from a new view point.