More than half a century has passed since man first stood on the summit of Mount Everest, and the story of man's attempts to climb higher and higher unaided is one of the more colorful and exciting in medicine and physiology. The past few decades have seen an explosion in interest in mountain pursuits in general, as increasing numbers of people take to the mountains for day trips and on longer excursions. As a result, doctors face ever-expanding challenges in dealing with the changes in human physiology and particular medical conditions that arise from exposure to altitude. Building on the success and reputation of previous editions, the fourth edition of High Altitude Medicine and Physiology includes major changes in the scientific content, with updates in many areas. The area of genetics has assumed great importance, along with other advances in molecular biology and medicine, and these are incorporated throughout the text. There are also new or improved sections on women and children at high altitude, the role of vascular endothelial growth factor, neurological disorders at high altitude, athletic training using high altitude, high altitude pulmonary edema, and the problems of patients with pre-existing diseases. Other new features include summary boxes highlighting important concepts, and increased tabulation of key data for rapid reference. While the authors have added much new material, they have also prudently trimmed down the existing material so that the text is still easily manageable and accessible in this fourth edition. High Altitude Medicine and Physiology remains invaluable reading for any doctor accompanying an expedition to — or advising patients on a visit to — a high altitude area, and for those physicians and physiologists who study our dependence on oxygen.