AIM:To investigate the expression of matrix metall-oproteinases(MMP)in pterygium.METHODS:The expression differences of MMP-2,MMP-7 and MMP-9 between human pterygium and the normal conjunctiva tissue were compared with immunohistochemical technique.RESULTS:MMP-2,MMP-7 and MMP-9 were expressed on all layers of pterygium.MMP-2 and MMP-7 were strongly expressed in hemoendothelial layer and squamous epithelium.MMP-9 was expressed in hemoendothelial layer.The positive expression of MMP-2,MMP-7 and MMP-9 in pterygium was stronger than that in the normal conjunctiva tissue(P<0.01).CONCLUSION:Over-expression of MMP may play an important role in the pathogenesis and relapse of pterygium.