My introduction to high altitude occurred in 1960 when I learned that Sir Edmund Hillary was planning a physiological expedition to the Himalayas. I applied to the scientific leader Dr. Griffith Pugh and was accepted in spite of the fact that I had previously never done any climbing. The Silver Hut Expedition as it was called was unique in that a small group of physiologists spent several months during the winter and spring of 1960–1961 at an altitude of 5,800 m (19,000 ft), about 16 km south of Mt. Everest. There, we carried out an extensive physiological program on acclimatization in a sophisticated, well-insulated wooden building that was painted silver. As far as we were aware, nobody had lived for such a long period at such a high altitude before. Subsequently, measurements were extended up to an altitude of 7,440 m (24,400 ft) on Mt. Makalu, which has an altitude of 8,481 m. These included the highest measurements of maximal oxygen uptake that have been reported to date . The physiological program was very productive with many articles in top-level journals .The primary purpose of the physiological program was to obtain a better understanding of the acclimatization process of lowlanders while they were living continuously at a very high altitude. The main areas of study were the cardiorespiratory responses to exercise under these conditions of extreme hypoxia, but measurements of blood, renal, and neuropsychometric function were made as well . However, in the event, there was an unrelenting rapid loss of body weight, and the conclusion was that we would not have been able to remain at that altitude indefinitely.The success of this expedition prompted me to wonder whether it might be possible to obtain physiological measurements at the highest point on earth. There was abundant evidence that at this altitude, humans are very close to the limit of oxygen deprivation, and so, it was a fascinating physiological problem to determine how the body responds.