Atherosclerosis is now widely recognized as a chronic inflammatory disease that involves innate and adaptive immune responses. Both cellular and humoral components of the immune system have been implicated in atherogenesis. Growing evidence suggests that immune cells play crucial roles in atherogenic plaque formation. Vulnerability of the plaque probably plays an important role in rupture. Most ruptures occur at the periphery of the fibrous cap that covers the lipid-rich core-points where the cap is usually thinnest and most heavily infiltrated by macrophage foam cells. Sudden rupture of a plaque triggers unstable angina, acute myocardial infarction, and sudden cardiac death. Initiation of collagen breakdown in plaques requires matrix metalloproteinase (MMP) family members including MMP-1, MMP-8, and MMP- 13. In addition, other MMPs such as MMP-2, -3, -9, -10 and -12 have also been reported to play roles in atherosclerosis. This review aims to focus on description of general structural features of MMPs and their roles in atherosclerosis.