Objective:To explore the expression of MMP-9 in mouse brain tissue and its significance.Methods: Cryptococcosis suspension alone (fungal suspension group) or combined with aprotinin (aprotinin group) was injected in to female C57BL/6 mice via femoral vein cannulation.The expression of MMP-9 was examined immunohistochemically 8 h later.Meanwhile,the mouse brain tissue homogenate colony count (CFU) was observed and the results were compared with that of the immunohistochemical examination.Results: The expression of MMP-9 was markedly increased in the fungal suspension group compared with the normal control group (P＜0.01); the expression in the aprotinin group was not significantly different from that of the normal control group (P＞0.05).The amount of cryptococcosis in the brain tissue was positively correlated with expression of MMP-9.Conclusion: MMP-9 is overexpressed in the brain of mice with Cryptococcal meningitis; MMP-9 might lead to increased permeability of blood brain barrier.