NCI researchers are collaborating with investigators in the Breast Cancer Association Consortium (BCAC), an international multidisciplinary consortium conducting studies with the aim of identifying genes that may be related to the risk of breast cancer. This consortium includes investigators from the U.S., Canada, Australia, Europe (the United Kingdom, Poland, Denmark, Finland), and Asia. Analyses within this consortium include identifying genetic and non-genetic risk factors related to breast cancer and mammographic density. Recently, NCI researchers pooled and analyzed data for over 35,000 breast cancer cases contributed by 34 studies in the BCAC to validate findings from the Polish Breast Cancer Study, which found that several breast cancer risk factor associations differed by tumor subtypes. Data from the BCAC analysis clarified results of prior smaller studies by establishing that risk factor associations varied by tumor hormone receptor status and that the most distinctive differences were found between luminal A and core basal phenotype (CBP) tumors. More information about this consortium may be found on the website, http://www.srl.cam.ac.uk/consortia/bcac/index.html.