The adhesion protein E-cadherin plays an important part in the process of epithelial morphogenesis. Expression of this protein is down regulated during the acquisition of metastatic potential in the late stages of epithelial tumor progression. There is evidence for transcriptional blockage of E-cadherin gene expression in this process. The transcription factor snail, which is expressed by f ibroblasts and some E-cadherin-negative epithelial tumor cell lines, represses transcription of E-cadherin. Metastasin (also referred to as mts-1, S100A4) in the control of cell motility as well as in cancer invasion and metastasis has now been extensively studied in numerous tumors. In this study, we examined the expression of E-cadherin, related proteins, snail and metastasin by western blot and RT-PCR in the oral squamous cell carcinoma cells. Immunohistochemical staining of oral squamous cell carcinomas was conducted to identify metastasin. It was found that E-cadherin was not recognized in 4 cell lines in grade 4D. RT-PCR analyses showed that snail and metastasin were expressed strongly in grade 4D cell lines. By immunohistochemical analysis, metastasin was highly detected in invasive cases. It is concluded that cell-cell adhesion would be decreased, and that E-cadherin may plays an important role in the process of invasion and metastasis. Snail further represses transcription of E-cadberin, and metastasin correlates with tumor invasion and metastasis in oral squamous cell carcinomas.