Background: Meningioma is a common intracranial tumor arising from the meningothelial (arachnoid) cells. Meningiomas are divided into 15 histological subtypes and three grades, including benign (grade I), atypical (grade II) and anaplastic (grade III). It is important to correctly decide whether a meningioma isbrain-invasive or not. Tumor invasion can be described as a stepwise process involving the degradation of the extracellular matrix (ECM), tumor cell adhesion to resident cells or components, increased proliferation, and cell migration into new intracellular/ECM space. It is believed that expression of Matrix metalloproteinases (MMPs) can be related with this process, especially the matrix metalloproteinase-9 (MMP9). Objectives: Investigation of matrix metalloproteinase-9 expression in different grades of meningioma and correlate this expression with brain invasion. Patients and methods: Matrix metalloproteinase-9 immunostaining was studied in 50 specimens of meningioma using avidin-biotin peroxidase method. Results: The percentage of brain invasive was 5% as regard to MMP9 score 1 ,5% as regard MMP9 score 2,20% as regard MMP9 score 3,70% as regard MMP9 score 4. A significant positive correlation was found between MMP9score and brain invasion (p< 0.001). Conclusion: Increased MMP9 expression is correlated with brain invasion.