The proto-oncogene Ets-1 is a member of the Ets family of transcription factors which share a unique DNA binding domain, the Ets domain. Ets binding sites have been described on the promoters or enhancers of many proteinases and several Ets members transcriptionally regulate such promoters in transient cotransfection assays. Ets-1 is involved in both normal and pathological functions. Ets-1 is expressed in a variety of cells, including endothelial cells, vascular smooth muscle cells and epithelial cells. Ets-1 regulates the expression of several angiogenic and extracellular matrix remodeling factors promoting an invasive phenotype. The Ets family of transcription factors may play a role in the disease progression of breast cancer. In tumors, including breast neoplasia, Ets-1 expression is indicative of poorer prognosis. This review will summarize the role of Ets-1 in both the tumor cells, and the tumor endothelial cells as it relates to breast tumor growth and spread.