Objective     To investigate the expression of peroxisome proliferator-activated receptor γ (PPARγ) and proliferating cell nuclear antigen (PCNA) in oral squamous cell carcinoma (OSCC) tissue and its clinical significance.      Methods     SP immunohistochemical staining and flow cytometry were used to evaluate the expression levels of PPARγ and PCNA in the OSCC tissues

paracancerous mucosae (2 cm from the tumor margin)

and normal mucosae (≥5 cm from the tumor margin

no microscopic cancer invasion) from 50 cases.      Results     The positive expression rate of PPARγ in OSCC tissues (68.0%

34/50) was significantly higher than those in paracancerous mucosae (26.0%

13/50) and normal mucosae (2.0%

1/50) (P0.05). The positive expression rate of PCNA in OSCC tissues (72.0%

36/50) was significantly higher than those in paracancerous mucosae (26.0%

13/50) and normal mucosae (4.0%

2/50) (P0.05). The flow cytometry result showed that the expression of PPARγ in OSCC tissues (396.56±33.39) was significantly higher than those in paracancerous mucosae (333.36±15.93) and normal mucosae (289.28±13.80) (P0.01) and that the expression of PCNA in OSCC tissues (543.11±41.55) was significantly higher than those in paracancerous mucosae (456.97±23.86) and normal mucosae (409.40±40.07) (P0.01). The high expression of PPARγ and PCNA was positively correlated with poor differentiation and lymph node metastasis of OSCC (the correlation coefficients of PPARγ were 0.497 and 0.392

P0.05; the correlation coefficients of PCNA were 0.324 and 0.561

P0.05). There was a positive correlation between PPARγ expression and PCNA expression.      Conclusion     The expression of PPARγ and PCNA is increased in OSCC tissues

indicating that PPARγ and PCNA may be involved in the carcinogenesis and development of OSCC.