Abstract： Objective To investigate the relationship between the matrix metalloproteinase-3(MMP-3)and the stability of carotid artery plaque,and explore MMP-3's prediction role on the attack and relapse of acute ischemic cerebrovascular events.Methods 100 patients with the first ever acute cerebral infarction,100 patients with chronic cerebral circulation insufficiency(CCCI)and 40 persons without cerebrovascular diseases were enrolled in this study.According to the carotid ultrasound examination,100 cerebral infarction patients were divided into three subgroup: unstable plaque group(45 patients,mixed plaque,soft plaque),stable plaque group(35 patients,plaque Group)and endometrial coarse group(25patients).Matrix metalloproteinase-3(MMP-3)levels of all the subjects were measured by enzyme-linked immunosorbent assay(as basal level).All the subjects were followed up for one year to observe cerebral infarction events.Serum MMP-3 levels of each group,and the basic serum MMP-3 levels were compared among patients who were attacked or relapsed cerebral ischemic with those who had not been attack cerebral ischemic during this period of time.Results 5 patients in the cerebral infarction group had relapse (5%),2 patients in the CCCI group were attacked by cerebral ischemic(2%),and no one in the normal control group was attacked by cerebral ischemic.Serum MMP-3 levels in the acute cerebral infarction group were significantly higher than CCCI group,and both groups were significantly higher than normal control group (P ＜0.05).The basic serum MMP-3 levels in all patients who were attacked by cerebral ischemic were significantly higher than those who had not been attack by cerebral ischemic during this period of time(P ＜0.05).The serum MMP-3 levels of the unstable plaque group were significantly higher than stable plaque group.And both groups were significantly higher than endometrial coarse group(P ＜0.05).Conclusions Elevated levels of matrix metalloproteinase-3(MMP-3)might have something with the stability of carotid atherosclerotic plaque,and participate the attack and the relapse of acute cerebral infarction.Determination of MMP-3 might be used to predict the attack and relapse of acute cerebral infarction.