The effects of physical exercise on the status of bone mineralization for a population of lifetime athletes were investigated. The bone mineral content of the radii of experienced male tennis players was measured. The bone mass of the radius of the playing arm (mean, 1.37 g/cm) was greater than that of the nonplaying arm (mean, 1.23 g/cm) in all but one person. The results were compared with data for a nonathletic (normal) population. The quantity of bone mineral present in the playing arms of the athletic population was greater than that of the dominant arms of nonathletes, which suggests that playing tennis during a lifetime may produce a localized increase in bone mineralization that is greater than that found in nonathletes.