The aim of this study was to investigate the effects of the extreme environment of high altitude hypoxia on olfactory threshold. The study was conducted before, during, and after a scientific expedition to Mera Peak (5,800 m). The n-butanol test was used for the assessment of the magnitude of the olfactory threshold. The finding was that the olfactory threshold dramatically increased at high altitude. We conclude that there is a physiological adaptation of olfaction due to altitude-hypoxia.