The term “high-altitude illness” is used to describe the cerebral and pulmonary syndromes that can develop in unacclimatized persons shortly after ascent to high altitude. Acute mountain sickness and high-altitude cerebral edema refer to the cerebral abnormalities, and high-altitude pulmonary edema to the pulmonary abnormalities. Because millions of visitors travel to high-altitude locations each year, acute mountain sickness is a public health problem and has economic consequences, especially for the ski industry. High-altitude pulmonary edema and high-altitude cerebral edema, though uncommon, are potentially fatal. High-altitude illness also provides a useful model for studying the pathophysiological process of hypoxia in an . . .