Objective:To study the relationship of the expressions of p53 and mdm2 in leukoplakia cancer.Methods:RT-PCR was used to detect the mRNA of p53,mdm2 in patients with leukoplakia cancer.The frequencies of p53,mdm2 in peripheral blood were detected by flow cytometric analysis.Results:The expression of p53mRNA in normal oral mucosa,simple oral leukoplakia,no-simple oral leukoplakia and leukoplakia cancer were 7.7%,27.3%,33.3%,56.8%,respectively.The frequencies of p53 in normal oral mucosa,simple oral leukoplakia,no-simple oral leukoplakia and leukoplakia cancer were(0.3±0.1)%,(l.6±0.9)%,(1.9±1.1)%,(3.4±1.8)%.The expression of mdm2 mRNA in normal oral mucosa,simple oral leukoplakia,no-simple oral leukoplakia and leukoplakia cancer were 0.0%,6.8%,11.1%,37.8%,respectively.The frequencies of mdm2 in normal oral mucosa,simple oral leukoplakia,no-simple oral leukoplakia and leukoplakia cancer were(0.1±0.1)%,(0.8±0.6)%,(1.2±0.8)%,(1.2±0.8)%.There was a positively correlation between p53 mRNA and mdm2 mRNA.Conclusions:The positive rate of p53 and mdm2 cells in the peripheral blood increases in patients with leukoplakia cancer tissue and has positive correlation with the severity of leukoplakia cancer.