Localized osteoporosis in 25 long-term stroke patients was evaluated by means of measuring the combined cortical thickness in the humerus, radius and third metacarpal bones of both involved and noninvolved upper extremities. The combined cortical thickness was found to be consistently smaller on the involved side. Since the factors of weight bearing and calcium homeostasis were eliminated or controlled in this study, the authors were able to focus on the role of muscle pull as manifested by voluntary muscle function and spasticity in relation to the degree of cortical thinning. A smaller degree of cortical thinning was associated with better voluntary muscle function, but the relationship of spasticity to preservation of cortical thickness was not clear cut. The applicability of these techniques to the study of factors affecting localized osteoporosis is discussed.