AIM: To examine the expression and distribution of tumor necrosis factor-? (TNF-?), tumor necrosis factor receptor I (TNFR I) and apoptosis in oral lichen planus, and evaluate their roles and relation in the oral lichen. METHODS: Immunohistochemical technique and TUNEL were employed to study the expression of TNF-?, TNFR I and apoptosis in 50 cases of oral lichen planus and 10 normal oral mucosa specimens. RESULTS: Compared with the normal control group, TNF-? expression was upregulated in mononuclear cells in lamina propria and decreased in keratinocytes in oral lichen planus lesion ( P