Since some risk factors for increased breast cancer risk could be related to high production of reactive oxygen species during the metabolism of estrogens by catechol estrogens, or to the exposure to genotoxic compounds, and some of these toxic compounds are usually metabolized by GSTA2, we carried out a hospital based case-control study in a Caucasian Portuguese population (291 breast cancer patients without familiar history of breast cancer and 547 controls matched for age, sex and ethnicity) in order to evaluate the potential modifying role of three non-synonymous polymorphisms in the GSTA2 gene (P110S Ex 5+56C>T;, rs2234951; S112T Ex5+63G>C, rs2180314 and E210A Ex7+83A>C, rs6577) on the individual susceptibility to breast cancer.