Atherosclerosis is a slow and complex disease that typically starts in childhood and often progresses with age. Advanced atherosclerotic plaque is characterized by a thickened intimal layer and an asymmetrical lesion that encroaches into the lumen. Plaques can grow large enough to significantly reduce the blood's flow through an artery. If the blockage happens in blood vessels that feed the heart, heart attack may occur. Coronary artery bypass grafting (CABG) surgery is common in treating patients with blocked arteries. CABG surgery is one of the most frequently performed surgical procedures with greater than 500,000 coronary bypass operations performed each year around the world. Veins and arteries are commonly used as conduits in human CABG to improve blood flow to the heart muscle. However, since stenosis and occlusion rates of arterial and venous grafts are markedly different, doubts about the most appropriate conduits persist. Vein grafts interposed to arteries are susceptible to the development of accelerated atherosclerosis. The vessel wall is an integrated functional component of the circulatory system that shows different response to hemodynamic conditions and atherosclerosis plaque formation. Collagen and elastin, the most abundant extracellular matrix proteins of the vascular wall, are responsible for the characteristic mechanical properties, tensile strength and elasticity. Furthermore, the biomechanical properties of the vessel wall is strongly correlated with the biochemistry of collagen and elastin. In normal vascular wall, there is a balance between collagen and elastin levels. Normal collagen and elastin levels as well as their arrangement are essential for vascular wall integrity and function while degradation of collagen and elastin by matrix-metalloproteinases (MMPs), are suggested to contribute to extracellular matrix remodeling. The roles of MMPs, in particular MMP-2 and MMP-9, in cardiovascular disease have been well documented. We hypothesized that the differences in histology, macromolecular composition and MMP levels of arterial and venous conduits may contribute to their differences in their occlusion rates and graft failure. To investigate this hypothesis, MMP levels, elastin/collagen ratio and histology of radial artery (RA), the left internal mammary artery (LIMA) and saphenous vein (SV) were determined and compared to that of aorta. Specimens were obtained from 11 patients (38-66 years old) who underwent CABG. All patients signed an informed consent for use of their vessel pieces that remained unused in the procedure. MMP levels were evaluated for by zymography and densitometry. Collagen Key words : Coronary artery bypass grafting surgery, extracellular matrix, matrix-metalloproteinases, radial artery, the left internal mammary artery, saphenous vein