Objective To investigate the expression of loricrin（LOR） and cytochrome P450 3A5（CYP 3A5） in oral submucous fibrosis（OSF） and to evaluate their roles in the defending ability of epithelium mucosae. Methods The expression of LOR and CYP 3A5 was examined in the specimens of 66 OSF and 14 normal buccal mucosa samples by immunohistochemistry, and the protein and mRNA expression of them was detected by Western blot and reverse transcriptase-PCR（RT-PCR）. Results LOR was overexpressed in 42（63.6%） cases of OSF, and showed a significant difference only between the early and moderately stages of OSF（P
