40 patients with various types of osteoporosis, aged 17 to 76 years, were treated for 12 months with a new NaF-drug (Ossiplex-Retard, film tbl. 25 mg NaF plus 200 mg vitamine C). Daily dosage was 50-100 mg. Clinical symptoms, X-ray-status of the axial skeleton, alkaline serum phosphatase and the consumption of analgetics were used for assessment. 2/3 of the patients with presenile and steroid induced osteoporosis responded well to treatment, while those with osteogenesis imperfecta, idiopathic osteoporosis and plasmocytosis did not show clinical or radiological improvement. In senile osteoporosis, a physiological process of aging, should only be given NaF-treatment, if fractures without callus formation are present. Harmless side effects, (gastrointestinal intolerance in 15% and a painful tendoperiostosis syndrome in 12.5%), necessitated discontinuation of treatment in 3 cases. The NaF-drug with added vitamine C has less side effects than other NaF-containing compounds and should therefore be included as part of the therapeutical regimen of certain types of osteoporosis.