Objective:To evaluate the predicting value of the marker of endothelial injury:plasma matrix metalloproteinase-9(MMP-9) level on the progression of acute anterior circulating territory infarction progressing to malignant middle cerebral artery infarction(m-MCA). Methods:Eighty-five patients with acute anterior circulating territory infarction,in which 45 patients progressed to m-MCA,were collected and sampled consecutively. The plasma MMP-9 and C-reactive protein(CRP) of all patients were determined by means of ELISA and immunoturbidimetry,respectively,at admission. And the clinical characters and cranial CT features of the patients were analysed. Results:At admission,the plasma MMP-9 level in the patients with m-MCA(230.0 ± 60.5 ng/ml) was significantly higher than that in the patients with non m-MCA(174.0 ± 56.0 ng/ml)(P < 0.001),while the plasma CRP levels between m-MCA and non m-MCA patients had no significant difference(8.8 ± 3.8 ng/ml vs 8.5 ± 4.0 ng/ml,P > 0.05). The sensitivity and specificity of serum MMP-9≥220 ng/ml to predict m-MCA were 89% and 95%, respectively. Conclusion:The increased level of plasma MMP-9 may be a predictor to the m-MCA proceeding.