The role of lipoprotein (a) in the atherosclerotic process is continually being unraveled, and many of its potential proatherogenic and prothrombotic features have already been elucidated. Whereas most studies have demonstrated a strong association between lipoprotein (a) and the presence and severity of coronary heart disease, other groups have failed to observe such a relationship, which does question the importance of this particle in promoting atherosclerosis. Evidence from a study of human coronary atherosclerosis appears to demonstrate that the pathogenicity of lipoprotein (a) is modulated by concomitant LDL-cholesterol levels. Such a modulation of the pathogenicity of lipoprotein (a) may underlie the conflicting results regarding its association with coronary heart disease. This article will examine this possibility, and will also outline the potential mechanisms through which lipoprotein (a) may interact with LDL to exert its adverse effects. As a consequence of its interaction with LDL, alternative strategies for treating high levels of lipoprotein (a) will be discussed.