This study demonstrates that in the course from the normal state to simple epithelial hyperplasia to epithelial dysplasia and to squamous cell carcinoma, caspase-3 expression showed a tendency toward a gradual increase in both groups, indicating that the caspase-3 expression level may be consistent with the progression form pre-oral cancerous changes to squamous cell carcinoma. This evidence concerns the gene CASP3 and squamous cell carcinoma.