ABSTRACT.Three male endurance athletes, 72‐74 years of age and holders of age‐group world track records, were selected for a detailed study of their body composition and physiological responses at rest and during exercise. In an attempt to better understand the process of aging and training in an aged population, comparisons were made with data from the normal population of similar age and with data from younger endurance athletes.The relative fat of these three athletes was well below the normal value for their age and approximate values seen in young endurance athletes. Their values for VC, FEV1.0, RV and TLC were within the normal range for their age, but well below those values reported for young endurance athletes. &OV0312;o2max and &OV0312;e were ˜ 50% and 60% respectively of the values obtained in young endurance athletes but ˜ 30‐40% greater than that seen in the normal, age‐matched population. The significance of these findings is discussed.