Abstract: Objective Aberrant methylation of tumor suppressor genes plays an important role in the development of colorectal cancers(CRC). The objective of this study was to identify the epigenetic changes in CRC. Methods Methylation-specific polymerase chain reaction (MSP) analysis was used on 28 cases of normal colorectal tissues, 36 cases of adenomatous polyp tissues, 73 matched CRC tumors and adjacent normal tissues. Results The unc5c promoter was hypermethylated in 75％(55/73)colorectal cancer tissues, 7 ％(5/73)adjacent normal tissues and 63％(23/36) adenomatous polyp tissues, but not in normal tissues. The frequency of unc5c promoter methylation in CRC and adenomatous polyp tissues was significantly higher than that in adjacent normal tissues (P<0.05). The methylation status of unc5c gene was associated with age, histology and tumor stage(TNM). Conclusion Our data suggested that unc5c gene promoter was frequently hypermethylated. Aberrant methylation of unc5c gene promoter may play a role in the development of CRC. Detection of the aberrant methylation of unc5c gene in tissues DNA from CRC patients might offer an effective means for the earlier auxiliary diagnosis of the