Radiographs of vertical sections cut through the centre of vertebral bodies and the middle of the remaining left half vertebra were used in a study of the structural changes of cancellous bone with age. The trabeculae were counted in two ways: (a) the number of transverse trabeculae which crossed the mid-line of the vertebra, and (b) all bone spicules in the central area of a specimen. Transverse trabeculae diminished steadily throughout life in the mid-sectlon, but were not affected in the lateral section. The area count in the mid-section showed no change in the trabeculae until 50 years, after which a progressive loss occurred. In the lateral section no change was observed in the area count.