Abstract: To gain a better understanding of brain tumor angiogenesis, new techniques for isolating brain endothelial cells (ECs) and evaluating gene expression patterns were developed. When transcripts from brain ECS derived from normal and malignant colorectal tissues were compared with transcripts from non-endothelial cells, genes predominantly expressed in the endothelium were identified. Comparison between normal- and tumor-derived endothelium revealed genes that were specifically elevated in tumor-associated brain endothelium. These results confirm that neoplastic and normal endothelium in human brains are distinct at the molecular level, and have significant implications for the development of anti-angiogenic therapies in the future.