The migration of vascular smooth muscle cells (VSMC) and the production of matrix metallopreteinases-9 (MMP-9) may play a key role in the development of atherosclerosis. In this study, we have more extensively investigated the inhibitory effect of UR on MMP-9 activity and TNF-${alpha}$ induced human aortic smooth muscle cells (HASMC) migration. The result from gelatin zymography showed that UR inhibited MMP-9 activity in a dose-dependent manner (IC50 = 55 g/ml). In addition, UR strongly inhibited the migration of HASMC induced by TNF-treatment (IC50 = 125 g/ml), although it has very low cytotoxic effect on HASMC (IC50 > 500 g/ml). These results suggest that UR is a potential anti-atherosclerotic agent through inhibition of MMP-9 activity and VSMC migration.