Lipoprotein(a) has many similarities to low density lipoproteins but possesses a unique protein moiety called apolipoprotein(a). The plasma concentration of lipoprotein(a) is mainly under genetic control and most of diets and hypolipidemic drugs do not change its level. Only nicotinic acid and neomycin are able to reduce its concentration. Epidemiological studies suggest that high level (greater than 30 mg/dl) of lipoprotein(a) is an independent risk factor for atherosclerosis of the coronary and carotid arteries. The risk is highest in patients with hypercholesterolemia. The atherogenic role of lipoprotein(a) is attributed to the lack of its recognition by the cellular receptors and its consequent diversion to the atherogenic "non receptor" pathway. Due to its strong homology with plasminogen, lipoprotein(a) could also favour thrombosis. It is suggested that its determination is of importance when evaluating a patient with atherosclerosis. Reducing high plasma levels of cholesterolemia appears to be mandatory when plasma lipoprotein(a) concentration is higher than 30 mg/dl.