Lipoprotein(a) [Lp(a)] is a unique lipoprotein that has emerged as an independent risk factor for developing vascular disease. Plasma Lp(a) levels above the common cut-off level of 300 mg/L place individuals at risk of developing heart disease particularly if combined with other lipid and thrombogenic risk factors. Studies in humans have shown Lp(a) levels to be hugely variable and under strict genetic control, largely by the apolipoprotein(a) [apo(a)] gene. In general, Lp(a) levels have proven difficult to manipulate, although some factors have been identified that can influence levels. Research has shown that Lp(a) has a high affinity for the arterial wall and displays many athero-thrombogenic properties. While a definite function for Lp(a) has not been identified, the last two decades of research have provided much information on the biology and clinical importance of Lp(a).