The arrangement of mineral within tabecular bone contributes significantly to the strength of the bone. Images of appendicular trabecular bone structure can be obtained using peripheral Quantitated Computed Tomography (pQCT) or Magnetic Resonance Imaging (MRI) devices. From such images, trabecular bone structure can be quantitated in a variety of ways. One such system measures the connectivity of trabeculae, the average dimensions of the holes in the trabecular bone structure and the area of the largest hole observed in the imaged plane. As measured by pQCT the values for these variables in 114 normal ambulatory men and women show the expected patterns of age dependence. While connectivity declines with aging in women it is relatively preserved in men. The mean hole area is greater in women especially in a small sub-group of mainly elderly women in whom it is raised by an order of magnitude. The maximum hole are shows little difference between genders and increases at a rate of about 0.6mm²y^-1 . The same variables measured by MRI in 23 normal subjects show similar results for connectivity and mean hole area. The maximum hole area detected with MRI is smaller than with pQCT and the rate of increase with age is less. This apparent difference may be due to the small number of subjects measured with MRI or the differences in anatomical location and orientation pQCT and MRI images. Measures of bone structure may improve the estimation of fracture risk in individual patients.