Abstract： Objective To examine the expressions of human telomerase reverse transcriptase (hTERT),p53 and MIB- 1 proteins in oral squamous cell carcinoma (OSCC) and to elucidate their significance. Methods Immunohistochemical (IHC) staining was used to detect the expressions of hTERT,p53 and MIB- 1 in 20 cases of oral usual mucosal hyperplasia,35 cases of atypical hyperplasia (mild∶ moderate∶ severe=10∶ 10∶15 cases) and 50 cases with OSCC of various differentiations (well differentiated∶ moderate differentiated∶ poorly differentiated=15 ∶ 20∶ 15 cases).Results hTERT,p53 and MIB-1 had different expressions in oral usual mucosal hyperplasia,atypical hyperplasia and OSCC of various differentiations.The positive expression rate of OSCC [hTERT of moderate differentiated OSCC:60％ ( 12/20 ) ] was higher than that of usual hyperplasia [ hTERT:10％ (2/20) ] and atypical hyperplasia [ hTERT of moderate atypical hyperplasia:30％(3/10) ].Notably,the positive expression rate of poorly differentiated OSCC [hTERT:66.7％ (10/15) ] was significantly higher than that of well differentiated OSCC [hTERT:46.7％ (7/15) ].Conclusion hTERT,p53 and MIB- 1 play important roles in the occurrence and development of OSCC and are closely associated with the differentiation degrees,which may be favorable markers for prognosis of OSCC.