Objective: To evaluate the expression of tissue repair gene MGMT by comparing normal and neoplastic colonic mucosa in patients with colorectal cancer (CRC). Methods: We studied 44 patients with colorectal cancer confirmed by histopathology. We excluded patients suspected of belonging to families with hereditary colorectal cancer (HNPCC and FAP) and patients with cancer of the lower or medium rectum treated with neoadjuvant chemoradiotherapy. The MGMT gene expression was assessed by the technique of polymerase chain reaction in real time (RT-PCR). The comparison of results for MGMT gene expression between normal and neoplastic tissues was made by paired Student's t test, adopting a significance level of 5% (p <0.05). Results: Tissue expression of the MGMT gene in all patients was lower in tumor tissue when compared to normal tissue (p = 0.002). 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