Objective:To explore the expression and significance of bcl-2 in oral lichen planus(OLP) and oral squamous cell carcinoma(OSCC).Methods:Immunohistochemical SP method was applied to detect the expression of bcl-2 in erosive,non-erosive OLP and well,moderate,poorly differentiated OSCC.Results:Expression of bcl-2 in NOM epithelium increased more than in OLP and the difference was statistically significant.Expression of bcl-2 in well,moderate and poorly differentiated OSCC were also significantly different.The better the OSCC differentiated,the stronger the bcl-2 expressed;the poorer the OSCC differentiated,the weaker the bcl-2 expressed.Conclusion:Expression of bcl-2 in OLP epithelium significantly less than in NOM epithelium, which may be associated with increased apoptosis of epithelial cells and epithelial thinning in the OLP.Expression of bcl-2 in well,moderate and poorly differentiated OSCC were significantly different,which may be related to the differentiation of OSCC.