Breast cancer is a significant cause of morbidity and mortality in Western countries. In the present work the distribution of genotypes and frequency of alleles of the RAD51 G/C polymorphism and the frequency of BRCA1 germ-line mutations in patients with breast cancer were investigated. One hundred breast cancer women provided blood for mutation analysis. Blood samples from age matched healthy individuals (n=106) served as control. The G/C polymorphism and BRCA1 mutations were determined by PCR-RFLP methods. The distribution of the genotypes of the G/C polymorphism RAD51 in both control and patients did not differ significantly (P>0.05) from those predicted by the Hardy-Weinberg distribution. There were no significant differences in the genotype distributions and allele frequencies between node-positive and node-negative patients. In the present study one Ex20insC mutation of BRCA1 gene was identified in women with breast cancer. Our study implies that the G/C polymorphism of the RAD51 gene may not be directly involved in the development and/or progression of breast cancer. The lack of detectable BRCA1 germ-line mutations in most cases suggests that there are probably additional, as yet unidentified genes predisposing to this disease.