Abstract: Objective 　To investigate the expression and activation of mitogen2activated protein kinase p38 and it s relationship with clinicopathological characters in nonsmall cell lung cancer. Methods 　Samples were obtained f rom 52 patient s with non2small cell lung cancer. Western blot was used to measure the ac2 tivation and expression of p38 and P2p38. Immunohistochemist ry was used for localization of p38 and P2 p38. Results 　In all 52 samples, the expression level of P2p38 in lung cancer tissues increased, which was 2. 1 times as high as compared with those in adjacent normal tissues ( P < 0. 01), but there were no differ2 ence of the level of p38. The expression level of P2p38 was found no correlativity with tumor size, TNM staging, lymph node metastasis and pathologic type. Immunohistochemist ry showed that P2p38 was loca2 ted in both nucleus and cytoplasm, and p38 was found only in cytoplasm. Conclusion 　The overactivity of p38 may play an important role in the development of human non2small cell lung cancer.