Objective：To assess the differences among the expressions of p38 mitogen activated protein kinases (MAPK), phospho-p38MAPK and nuclear factor kappa B (NF-κB) in oral lichen planus (OLP) and oral squamous cell carcinoma(OSCC).Methods:In the study, 53 cases of OLP, 45 of OSCC, and 18 controls were obtained and 4-μm-thick histological sections were prepared from formalin-fixed paraffin-embedded tissue blocks.The expressions of p38MAPK,phospho-p38MAPK and NF-κB were detected by immunohistochemistry staining. Furthermore, the expressions of p38MAPK and phospho-p38MAPK were detected using Western blotting analyses in the fresh tissues from 11 cases of OLP, 5 cases of OSCC, and 7 cases of the controls. Results:p38MAPK was over-expressed in the lamina propria, but lowly expressed in the epithelium in OLP group. Phosphop38MAPK was lower expressed in OLP group than in OSCC and control groups.NF-κB was found over-expressed in the lamina propria in OLP group.p38MAPK was found expressed in all the samples in the 3 groups. The expression of phospho-p38MAPK was observed in 8 (8/11) OLP samples, 5 (5/5) OSCC samples and 4 (4/7) controls by Western blotting, but no significant differences were found within the 3 groups. Conclusion:p38MAPK can be detected in normal oral mucosa, OLP and OSCC.phospho-p38MAPK may be related to the onset and progression of OSCC. The role of p38MAPK in OLP is yet to be revealed.