This proposal is to request support for a Keystone Symposia meeting entitled "Hypoxia: Molecular Mechanisms of Oxygen Sensing and Response Pathways", organized by Navdeep S. Chandel, Peter J. Ratcliffe, Volker H. Haase and Agnes G"rlach, which will be held in Keystone, Colorado from January 19 - 24, 2010. Molecular oxygen is absolutely essential for cellular respiration and higher organisms have developed sophisticated physiological responses that allow adaptation to a low oxygen environment. These include neurotransmitter release from the carotid body to increase respiration;pulmonary vascular constriction to redirect blood flow from poorly to well oxygenated regions;and in the kidney, enhanced erythropoietin secretion to boost red blood cell production to augment oxygen carrying capacity. Tissue hypoxia is not only associated with a variety of pathological conditions such as pulmonary, cardiovascular and neoplastic diseases, but also occurs during normal embryonic development and plays an important role in stem cell maintenance. This meeting will highlight the latest, cutting-edge advances in hypoxia research and discuss (1) the cellular and molecular mechanisms that underlie physiological responses to hypoxia, (2) the role of hypoxic signaling in the pathogenesis and progression of pulmonary hypertension, ischemia and cancer, (3) the importance of hypoxia in stem cell maintenance and embryonic development, and (4) the overall state of the art in hypoxic signaling in inflammation and metabolism. (End of Abstract)