The San Antonio Breast Cancer Symposium is the largest annual meeting devoted solely to breast cancer research. The late William L McGuire's vision for this meeting was to stimulate 'translational research', many years before this term became popular. In this way, the San Antonio Breast Cancer Symposium represents a forum in which basic and clinical researchers present their research side by side. Each year sees the continued evolution of our understanding of the basic mechanisms of breast cancer initiation and progression, and the clinical application of this knowledge. Major topics of discussion at the symposium this year were the cell cycle, new evolving concepts of estrogen receptor action, breast cancer stem cells, new predictive and prognostic markers (including microarray studies), and continued exploration of the mechanisms of drug resistance. This report will summarize preclinical and translational highlights from the meeting.