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 colourful and exciting in medicine and physiology. The past few decades have seen an explosion in the interest in mountain pursuits in general, as increasing numbers of people take to the mountains for day trips and 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 and cold. Building on the success and reputation of previous editions the fourth edition 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 disease. Other new features include summary boxes highlighting important concepts, and increased tabulation of key data for rapid reference. Despite the addition of new material, the authors have avoided the text become unwieldy and less readable with prudent pruning of existing material. High Altitude Medicine and Physiology remains invaluable reading for any doctor accompanying an expedition to altitude or advising patients on a visit to altitude, and for those physicians and physiologists who study our dependence on oxygen. The aim of the highly-respected authors, joined following the retirement of Michael Ward by Robert Schoene - to provide a text that will help physicians continue to improve the health and safety of all people who visit, live or work in the cold, thin air of high mountains - is undoubtedly met by this new edition.