Abstract: Objective 　To understand the role of promoter methylation for hML H1 in non-small cell lung cancer. Methods 　The methylation status was determined by MSP (methyl-specific PCR), and RT-PCR was employed to measure mRNA level. Results 　The f requencies of methylation in NSCLC and corresponding non-neoplastic lung tissues were : 55 % and 14 % for hML H1. Methylation of hML H1 was more frequent in > 65 group ( P < 0. 01) . Methylation of hML H1 was more frequent in smoking group ( ( P <0. 05 or P < 0. 01) . Methylation of hML H1 was more f requent with TNM stage advanced ( P < 0. 05 or P< 0. 01) . The samples with methylated status showed the decline or loss of hML H1 mRNA t ranscription. 5-Aza-CdR could induce re-expression of the silenced methylated hML H1. Conclusion 　Promoter methylation is the predominant mechanism in hML H1 deregulation in NSCLC,but 5-Aza-CdR could reverse the gene transcriptional activity.