OBJECTIVE:The study was to investigate the expression features of p53 protein and PCNA antigens in premalignant lesions of oral mucosa and further to discuss its clinical significance.METHODS: 50 samples were retrieved from the biopsy of the patients with suspicious premalignancy.Followed by the diagnosis pathologically,the sections were labeled with p53 and PCNA antigens by immunohistochemistry. RESULTS: In premalignant lesions,the progression staining with p53 and PCNA antigens were positively corresponding to the epithelial dysplasia from the basal layer to the keratinous layer. CONCLUSION: The p53 and PCNA antigens expressed synchronously in premalignant lesions of oral mucosa and exhibited direct correlation with the degree of epithelial dysplasia;The positive signals with p53 and PCNA antigens in the premalignant lesions may be the earlier incidence in carcinogenesis, which may initiated at the earlier stage of epithelial dysplasia.This phenomenon is deserving of clinicians' attention for discovering the premalignant lesions earlier;The detection of p53 and PCNA antigens would be helpful to find out the lesion which has the tendency turning to dysplasia.