Pulmonary mechanics, ventilatory drive, and blood-oxygen transport are modified with age, but quantification of these changes and evaluation of their physiologic implications have been seriously limited. During acute and chronic physiologic stress, the respiratory and hemoglobin oxygen transport systems respond to facilitate tissue oxygenation. While these adaptive responses have been well documented in young adults, the level of their retention in the elderly is uncertain. Studies conducted to date have provided conflicting information. Some of this may have been the result of the limited number of subjects studied in each decade of life. Pulmonary and blood-biochemical changes occur gradually over many decades, necessitating evaluation of an appropriate population in order to establish optimal approaches for therapeutic treatment of the elderly and to develop a foundation for subsequent studies of the role of the cardiorespiratory system in the normal aging process. More studies of a longitudinal rather than cross-sectional nature are required before an adequate assessment of age-related alterations in function, capacity, or adaptative potential can be predicted.