Senile osteroporosis itself is asymptomatic unless pain is induced by the static insufficiency of the skeleton, in long lasting disease. Conventional procedures for early diagnosis and control of patients are invasive and therefore not suitable for routine purposes. The efficiency of sodium fluoride for the treatment of senile osteoporosis after a minimum of 12 months has been established by invasive methods. It is the purpose of this study, to examine the value of photoabsorption-densitometry with double-isotope-method (125-J, 241-Am) for the evaluation of a therapeutic effect in this disorder. 7 patients with clinical and radiological evidence of senile osteoporosis (6 female, 1 male patient with ages of 56 to 87 years) underwent regular follow-up examinations for one year while on a regimen of 25mg. sodium fluoride, as retard, twice daily. The bone mineral content registered 1 cm. proximal of the proc. styloideus ulnaris (representative for the trabecular bone) and 8 cm proximal from the proc. styloideus ulnaris of the right forearm (representative for cortical bone) was not statistically different from the measurements registered prior to the study. However, the bone mineral content registered in both regions increased significantly, after 12 months treatment (p less than 0.05). This indicates that the assessment of bone mineral content by photonabsorptiondensitometry is a valuable method for therapeutic control of this disorder. The method is recommended as a routine procedure for the early diagnosis and for follow up of sodium fluoride therapy geriatric patients.