Nibrin, encoded by the NBN gene, participates in DNA repair. Mutations in the NBN gene lead to Nijemen breakage syndrome, which may result in several types of diseases, particularly susceptibility to cancer, including breast cancer. Polymorphic variants and defective mutations occurring in the NBN gene increase the risk of breast cancer through the double-stranded break repair mechanism. The aim of the present study was to investigate a possible association between breast cancer and NBN genetic variants, NBN 924 T>C, 8360 G>C and 30537 G>C, in women with breast cancer. Locus-specific primers were designed to study 3 genetic variants in DNA samples isolated from peripheral blood samples of 101 women with breast cancer and 115 healthy controls. Subsequently, 3 polymerase chain reaction-restriction fragment length polymorphism methods were performed and the obtained results were statistically analysed. The NBN gene 924 T>C variant was found to be significantly associated with breast cancer (chi(2)=5.722, P=0.017). There were no statistically significant differences between cases and controls in the NBN gene 8360 G>C variant (chi(2)=1,125, P=0.570) or the NBN gene 30537 G>C variant (chi(2)=4.301, P=0.116). In conclusion, the NBN gene 924 T>C variant may be a genetic risk factor for breast cancer development in women with breast cancer.