To gain a better understanding of breast tumor angiogenesis, breast endothelial cells (ECs) were isolated and evaluated for gene expression patterns. When transcripts from breast ECs derived from normal and malignant breast tissues were compared, genes that were specifically elevated in tumor-associated breast endothelium were revealed. These results confirm that neoplastic and normal endothelium in human breast are distinct at the molecular level, and have significant implications for the development of anti-angiogenic therapies in the future.