Overall, a significant association was found between the combined effects of GSTM1 present/null and GSTP1 IIe105Val polymorphisms on BC risk (GSTM1 null/GSTP1 IIe/IIe + GSTM1 present/GSTP1 Val* vs. GSTM1 present/GSTP1 IIe/IIe: OR = 1.14, 95% CI = 1.00–1.31, GSTM1 null/GSTP1 Val* vs. GSTM1 present/GSTP1 IIe/IIe: OR = 1.58, 95% CI = 1.21–2.06, all risk genotypes vs. GSTM1 present/GSTP1 IIe/IIe: OR = 1.28, 95% CI = 1.08–1.52, GSTM1 null/GSTP1 Val* vs. (GSTM1 null/GSTP1 IIe/IIe + GSTM1 present/GSTP1 Val* + GSTM1 present/GSTP1 IIe/IIe): OR = 1.40, 95% CI = 1.12–1.75). Here, GSTM1 is linked to breast cancer.