Matrix metalloproteinase(MMP) is the proteolytic enzyme of the extracellular matrix. MMPs play a role in the invasion and metastasis of malignant tumor, but it is not known whether the expression of MMPs in squamous cell carcinoma of the tongue is related to the prognostic factors of this tumor. In this study, 32 paraffin-embedded tumor specimens were examined immunohistochemically using monoclonal antibodies of MMP-2, MMP-3, MMP-10 and MMP-13. The possible relationships between the expressions of the MMPs and TNM staging, the differentiation of tumor cells, size of tumor mass and lymph node metastasis were anlaysed statistically. The results were as follows. 1. The expression of MMP-2 increased according to TNM staging (P<0.05) and lymph node metastasis (P<0.05) and the expression of MMP-2 was not affected by the differentiation of tumor cells or tumor size. 2. The expression of MMP-3 increased with increasing tumor size (P<0.05). However it was not related to TNM staging, the differentiation of tumor cells or lymph node metastasis. 3. The expression of MMP-10 was unrelated to TNM staging, differentiation of tumor cells, lymph node metastasis or tumor size. 4. The expression of MMP-13 increased as tumor size increased (P<0.05). However it was not related to TNM staging, the differentiation of tumor cells or lymph node metastasis. We concluded that the expression patterns of MMP-2, MMP-3, and MMP-13 may play a role in the diagnosis, treatment plan and prognostic evaluation of malignant tumors of the tongue.