Oxygen is vital for the development and survival of mammals. In response to hypoxia, the brain initiates numerous adaptive responses at the organ level as well as at the molecular and cellular level, including the alteration of gene expression. Astrocytes play critical roles in the proper functioning of the brain, thus the manner in which astrocytes respond to hypoxia is likely important in determining the outcome of brain hypoxia. Here we have used microarray gene expression profiling and data analysis algorithms to identify and analyze hypoxia-responsive genes in primary human astrocytes. We have also compared the gene expression patterns in astrocytes with those in human HeLa cells and pulmonary artery endothelial cells (ECs). Remarkably, in astrocytes, 5 times as many genes are induced as suppressed, whereas in HeLa and pulmonary ECs, as many as or more genes are suppressed than induced. More genes encoding hypoxiainducible functions, such as glycolytic enzymes and angiogenic growth factors, are strongly induced in astrocytes, compared to HeLa cells. Further, gene ontology and computational algorithms reveal that many target genes of the EGF and insulin signaling pathways and the transcriptional regulators Myc, Jun and p53 are selectively altered by hypoxia in astrocytes. Indeed, Western blotting analysis confirms that two major signal transducers mediating insulin and EGF action, Akt and MEK1/2, are activated by hypoxia in astrocytes. These results provide a global view of the signaling and regulatory network mediating oxygen regulation in human astrocytes.