We explored different expressions of matrix metalloproteinases (MMPs), tissue inhibitor of metalloproteinases (TIMPs) and plasminogen activators (PAs) in atherosclerotic occlusive and aneurysmal diseases. Aortic samples were obtained during operation for aortic aneurysm (n = 11), occlusive disease (n = 10), and from fresh cadavers (n = 3). We examined the expressions of MMPs, TIMPs, and PAs by zymography, Western blotting and immunohistochemistry. Immunoblotting analysis showed that MMP-2 was expressed in atherosclerotic plaque > aneurysmal wall > normal aorta, and that MMP-9 and TIMP-1 expressions were increased in aneurysmal wall compared to atherosclerotic plaque or normal aorta. Urokinase-type PA (uPA) was expressed in atherosclerotic plaque, but tissue-type PA (tPA) expression was increased in aneurysmal wall. Gelatin-zymograms showed that both latent and activated forms of MMP-2 were increased in atherosclerotic plaque. Atherosclerotic plaque had increased expression of immunoreactive MMP-2 in the media and the adventitia. The presence of macrophages, detected by immunohistochemistry in the adventitia of higher MMP-9 and TIMP-1 expressions in aneurysmal wall suggests that these cells are a possible source of MMP-9 and TIMP-1. These findings suggest that the increased expressions of MMP-2 and uPA may play a role in the formation of atherosclerotic occlusive disease, and that MMP-9, TIMP-1 and tPA expressions do in atherosclerotic aneurysmal formation.