Colorectal cancer is one of the most commonly diagnosed cancer and a leading cause of death from cancer. DNA repair defects have been associated with an individual susceptibility to cancer. Therefore, polymorphisms of DNA repair genes, including XRCC1 gene, are suspected to may increase the risk of colorectal cancer.The aim of the study was to examine the association between Arg399Gln polymorphisms of XRCC1 gene and the occurrence of colorectal cancer. Research and understanding of the molecular basis of the formation of colorectal cancer will allow for typing of genetically loaded persons and qualifying them to a high-risk group.Material and methods. In case-control study we genotyped 150 colorectal cancer patients and 170 healthy subjects from Polish population. Analysis was performed by PCR-restriction fragment length polymorphism (PCR-RFLP).Results. We found that Gln/Gln genotype is associated with increased risk of colorectal cancer (OR 1.984; Cl 95% 1.070-3.677; p=0.029). We also found that Arg/Gln genotype is a risk factor for progression of tumor growth (OR 3.52; Cl 95% 1.157-10.707; p=0.023).Conclusions. The current state of research suggests a link between Arg399Gln XRCC1 polymorphism and increased risk of colorectal cancer. Therefore, we conclude that the Arg399Gln polymorphism of XRCC1 gene may underlie at the molecular basis of the causes of colorectal cancer.