This monograph contains the proceedings of a symposium entitled, "Tissue Hypoxia and Ischemia," which was held at the Annenberg Center of the University of Pennsylvania on August 13 and 14, 1976. The symposium was jointly sponsored by the following groups at the University of Pennsylvania: the Respiratory Physiology Group of the Department of Physio­ logy, the Cardiopulmonary Section of the Department of Medicine, the Johnson Research Foundation, the Cerebrovascular Research Center of the Department of Neurology, the Head Injury Center of the Department of Neurosurgery, the. Institute for Environ­ mental Medicine, and the International Society on Oxygen Transport to Tissues. Its purpose was to promote an interdisciplinary discussion of oxygen sensors in various tissues and their mechanism of action as well as to examine the deleterious effects of hypoxia and ischemia with special reference to the brain. There were four sessions, one on the biochemistry of physi­ ologic oxygen sensors, two on the mechanism of oxygen sensing in tissues and one on the circulatory and metabolic aspects of cerebral hypoxia and ischemia.