This volume of Breast Disease is dedicated to the emerging science using high-throughput genomic approaches to study breast cancer. These technologies offer great potential for stratifying the classification and treatment of patients based upon individual molecular profiles as well as identifying important new targets for therapy. The application of gene expression profiling to breast cancer research has already revolutionized clinical oncology and is being vigorously applied by the pharmaceutical industry for translational research. The contributors to this volume of Breast Disease have made important advances in the field of breast cancer research from both the basic science and clinical oncology perspectives. Genomic approaches based upon single nucleotide polymorphisms (SNPs) are being used to identify genetic loci that contribute to breast cancer development and progression (see Struewing). Important molecular distinctions between a large panel of cancer cell lines have been identified using expression profiling and the identified gene clusters may be related to the biologic responses of the cell lines to a panel of over 100,000 screened compounds (see Weinstein). This serves as a proof-of-principle that such comprehensive and integrated genomic approaches can be successfully utilized. These types of approaches to cancer and pharmacogenomics will greatly accelerate drug discovery and individualized therapy.