The vascular endothelial growth factor (VEGF) plays a crucial role in the initiation of angiogenesis, which is an important stage in tumor development. A functional 936_C>T polymorphism in the VEGF gene and its association with sporadic breast cancer risk has been analyzed in various studies yielding conflicting results. To analyze the role of this polymorphism in modifying hereditary breast and ovarian cancer risks, we conducted a case-control study and genotyped 755 Polish BRCA1 carriers, including 319 breast cancer cases, 146 ovarian cancer cases, and 290 unaffected controls. The results revealed an association of the CT+TT genotypes with a reduced breast cancer risk (OR(adj) 0.63, 95% CI, 0.41-0.98; OR(clustered) 0.63, 95% CI, 0.48-0.83), and a potential effect on ovarian cancer risk (OR(adj) 0.62, 95% CI, 0.33-1.18; OR(clustered) 0.62, 95% CI, 0.47-0.83). Thus, the 936_C>T polymorphism appears to modify disease risks in BRCA1 carriers.