In the age-adjusted and unadjusted models, XRCC1 399Q was associated with a marginally significant decrease in breast cancer risk in the dominant model (XRCC1 399 R/Q + Q/Q vs. R/R, unadjusted OR: 0.64, 95% CI: 0.41-1.00; age-adjusted OR: 0.65, 95% CI: 0.42-1.02.XRCC1 399Q was also associated with a marginally significant decrease in risk in the co-dominant models (XRCC1 399 Q/Q vs. R/R, age-adjusted OR: 0.44, 95% CI: 0.20-0.96; multivariable-adjusted OR: 0.44, 95% CI: 0.18 - 1.11). This evidence concerns the gene XRCC1 and breast carcinoma.