Thus, in the present analysis, we examined the association between the two non-synonymous polymorphisms in XRCC1 that have been shown to have functional relevance in DNA repair capacity (Arg194Trp (rs1799782) and Arg399Gln (rs25487)) and postmenopausal breast cancer risk in a case-control study nested in the American Cancer Society Cancer Prevention Study II (CPS-II) Nutrition Cohort. The gene discussed is XRCC1; the disease is breast cancer.