Microradioscopic study of metacarpals in 24 osteomalacic and 34 osteoporotic patients revealed excessive intracortical resorption (striations) in approximately 60 percent of patients suffering from osteomalacia, but in none of the osteoporotics. Phalangeal periosteal resorption was found less frequently in osteomalacia than metacarpal striations, and was absent in osteoporotics. On the other hand, quantitative evaluation of cortical thickness, percent cortical area, bone mineral mass, and density did not show any clear differences between the two study groups. It is concluded that the differential diagnosis between osteomalacia and osteoporosis may be considerably improved by microradioscopy of hand bones.