This study was aimed to investigate the expression of gelatinases (MMP-2 and MMP-9) in mesenchymal tumors and the roles they act during invasion and metastasis. 45 cases of bone and soft tissue tumors with various pathologic categories were subjected to immunohistochemistry and gelatin zymography analysis. The results showed that the positive immuno-staining ratio and the activity of both MMP-2 and MMP-9 were higher in malignant tumors than in benign tumors and normal tissue. In malignant tumors, the positive stained cells usually gathered in the marginal area of tumor foci or the invading area, or formed distinctive positive-stained cell clusters, indicating their relationship with the aggressive biologic behavior of this kind of malignant tumor.