Abstract GATA-binding protein 3 (GATA3) is a transcription factor that is crucial to mammary gland morphogenesis and differentiation of progenitor cells, and has been suggested to have a tumor suppressor function. The rs570613 single nucleotide polymorphism (SNP) in intron 4 of GATA3 was previously found to be associated with a reduction in breast cancer risk in the Cancer Genetic Markers of Susceptibility project and in pooled analysis of two case-control studies from Norway and Poland (P trend = 0.004), with some evidence for a stronger association with estrogen receptor (ER) negative tumours [Garcia-Closas M et al. (2007) Cancer Epidemiol Biomarkers Prev 16:2269–2275]. We genotyped GATA3 rs570613 in 6,388 cases and 4,995 controls from the Breast Cancer Association Consortium (BCAC) and 5,617 BRCA1 and BRCA2 carriers from the Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA). We found no association between this SNP and breast cancer risk in BCAC cases overall (ORper-allele = 1.00, 95% CI 0.94–1.05), in ER negative BCAC cases (ORper-allele = 1.02, 95% CI 0.91–1.13), in BRCA1 mutation carriers RRper-allele = 0.99, 95% CI 0.90–1.09) or BRCA2 mutation carriers (RRper-allele = 0.93, 95% CI 0.80–1.07). We conclude that there is no evidence that either GATA3 rs570613, or any variant in strong linkage disequilibrium with it, is associated with breast cancer risk in women. Sharon E. Johnatty1, Fergus J. Couch2, Zachary Fredericksen2, Robert Tarrell2, Amanda B. Spurdle1, Jonathan Beesley1, Xiaoqing Chen1, kConFab Investigators3, AOCS Group1, 3, The Swedish BRCA1 and BRCA2 Study Collaborators4, 5, Daphne Gschwantler-Kaulich6, Christian F. Singer6, Christine Fuerhauser6, Anneliese Fink-Retter6, Susan M. Domchek7, Katherine L. Nathanson7, Vernon S. Pankratz2, Noralane M. Lindor2, Andrew K. Godwin8, Maria A. Caligo9, John Hopper10, Melissa C. Southey10, Graham G. Giles11, Christina Justenhoven12, 13, Hiltrud Brauch12, 13, Ute Hamann14, Yon-Dschun Ko15, Tuomas Heikkinen16, Kirsimari Aaltonen16, 18, Kristiina Aittomäki17, Carl Blomqvist18, Heli Nevanlinna16, Per Hall19, Kamila Czene19, Jianjun Liu20, Susan Peock21, Margaret Cook21, Radka Platte21, D. Gareth Evans22, Fiona Lalloo22, Rosalind Eeles23, Gabriella Pichert24, Diana Eccles25, Rosemarie Davidson26, Trevor Cole27, Jackie Cook28, Fiona Douglas29, Carol Chu30, Shirley Hodgson31, Joan Paterson32, Frans B. L. Hogervorst33, Matti A. Rookus34, Caroline Seynaeve35, Juul Wijnen36, Maaike Vreeswijk37, Marjolijn Ligtenberg38, Rob B. van der Luijt39, Theo A. M. van Os40, Hans J. P. Gille41, Marinus J. Blok42, HEBON33, Claudine Issacs43, Manjeet K. Humphreys21, Lesley McGuffog21, Sue Healey1, Olga Sinilnikova44, Antonis C. Antoniou21, Douglas F. Easton21, Georgia Chenevix-Trench1 and on behalf of the Breast Cancer Association Consortium and the Consortium of Investigators of Modifiers of BRCA1/245