The identification of two breast cancer predisposition genes, BRCA1 and BRCA2, in the mid-1990s has led to a better understanding of the molecular pathogenesis of hereditary breast cancer and to a new era in breast cancer research. The present article reviews the current state of knowledge regarding the biology of BRCA1 and BRCA2, the cancer risks associated with carrying a pathogenic mutation in either of these genes and the possible genetic and environmental risk modifiers. The phenotypes of BRCA1- and BRCA2-associated hereditary breast cancers are reviewed. Research into BRCA1- and BRCA2-associated breast cancer is in its infancy and much remains to be learned, particularly about modifiers of genetic risk and the clinical implications of carrying a mutation in one of these two genes. Australia has an excellent research infrastructure in place, through the Australian Breast Cancer Family Study and the Kathleen Cuningham Foundation Consortium for Research into Familial Breast Cancer, to contribute substantially to future research in this area.