In the present study, we found that the expression of NAT1 mRNA was significantly reduced in COAD tissues compared with the corresponding normal tissues, which contrast with observations for the methylation of NAT1. Correlation analysis showed that mean methylation in the promoter region of NAT1 was negatively correlated with NAT1 mRNA expression, suggesting that NAT1 may function as a tumor suppressor gene, and that a high level of methylation could reduce the mRNA expression of this gene in COAD tissues. This evidence concerns the gene NAT1 and neoplasm.