To date, estrogen receptor, progestogen receptor, and HER2/neu represent molecular biomarkers currently used in routine clinical practice to aid treatment decisions. Over the last few years, a large body of preclinical and retrospective clinical data has accumulated that suggests that BRCA1 mutation functions as a novel predictive marker of response to chemotherapy. This article reviews the role of BRCA1 as a predictive marker of chemotherapy response in breast cancer and examines the link between BRCA1 deficiency and the basal-like phenotype. Search strategy. Data for this article were identified through MEDLINE and PubMed searches for published reports using the terms BRCA1, breast cancer, basal-like, chemotherapy, prognosis, and predictive markers. In some cases, due to the restriction of space, readers are referred to review articles to allow further reading. Only articles published in English were included.