Tehran University of Medical Sciences Basic & Clinical Cancer Research 2228-6527 5 3 2013 07 01 23 27 Majid Motovali-Bashi Department of Genetics, Faculty of Medical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran Jafar Maleki Department of Biology, Faculty of Medical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran Simin Hemmati Department of Oncology and Radiotherapy, Faculty of Medical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran Hassan Korbekandi Department of Genetics and Molecular Biology, Faculty of Medical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran 2014 04 13 2014 09 28 Background: Colorectal cancer is the third cause of cancer death in western countries. Age, inadequate diet, obesity, inactivity and genetic changes are some of the risk factors of colorectal cancer. Correlation of genetic diversity in homologous recombination repair system with cancer was evaluated in many recent studies. This study was done to investigate the correlation of T241M polymorphism in XRCC3 gene and colorectal cancers. Materials and Methods: In this cross-sectional study, after collecting blood samples and extracting genomic DNA, genotype distribution of the polymorphism was determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Results: A significant correlation was observed between T241M polymorphism and colorectal cancer. Age and family history were also found to be correlated with this cancer. Although no statistically significant relationship has been found between smoking and colon cancer, our findings showed a correlation between smoking and rectum cancer. Furthermore, we observed that the most occurrence of metastatic activity was in the rectum. Conclusion: According to our study, T241M polymorphism in XRCC3 gene from homologous recombination (repair system??) could be a suitable factor for early diagnosis of colorectal cancer, while its co-operation with smoking is also regarded as a risk factor for rectum cancer. https://bccr.tums.ac.ir/index.php/bccrj/article/view/97 https://bccr.tums.ac.ir/index.php/bccrj/article/download/97/pdf