AIM: To examine the expressions and distribution of Caspase-3, TNF-α and TNFRI and their relationship to apoptosis in oral lichen planus (OLP). METHODS: Immunohistochemical staining with SP method and TUNEL technique were used to detect the expressions of Caspase-3, TNF-α and TNFRI in 33 cases of OLP and 7 cases of normal oral mucosa specimens (the controls). RESULTS: Compared with the controls, OLP was increased in apoptosis index (AI) of epithelial cells and decreased in AI of lymphocytes (both P<0.05). The expression of Caspase-3 in all OLP cases was significantly higher than that in the normal group both in the epithelial layer and in the lamina propria (P<0.025). Compared with that in the normal group, TNF-α expression in all OLP cases was decreased in the epithelial layer and increased in the lamina propria (both P<0.025), while TNFRI expression was increased in the epithelial layer and decreased in the lamina propria in all OLP cases(both P <0.025). TNF-α expression was significantly increased in the lamina propria in the erosion group compared with the non-erosion group (P<0.05). A positive correlation was observed between Caspase-3 expression and AI in the epithelial cells(r=0.631, P<0.05). However, there was no significant correlation between Caspase-3 expression and AI in lymphocytes (P >0.05). Expressions of TNF-α and TNFR1 were significantly correlated to AI both in the epithelial layer and in the lamina propria. CONCLUSION: The accelerated apoptosis of keratinocytes and the inhibition of lymphocyte apoptosis may coexist in OLP, which may contribute to the form ation and progression of OLP.