Abstract OBTAINING a respectable hatching percentage from the eggs of domestic poultry is one of the important problems of the poultry industry in areas of high elevation. This problem exists at Laramie, Wyoming, where the elevation is approximately 7,200 feet above sea level. The Wyoming Agricultural Experiment Station, highest in the United States, is an ideal location to study the problems of high-altitude incubation. One objective of the investigation reported in this paper was to reexamine the reported improvement in hatchability resulting from the use of supplemental oxygen in incubation. Another objective was to study the effect of oxygen concentration as it is related to selecting for genetic improvement in hatchability. North (1941) stated that the lower barometric pressure of Laramie lowers the volumetric concentration of oxygen by 25 percent and that more ventilation is required to supply the same amount of oxygen in the incubator. Thompson (1952) reported that at …