Considering that the Calcitonin is one of the main therapeutic means in the senile Osteoporosis, the authors go over and over the necessity of a simple diagnostic test in order to point out the sensitiveness and resistance to the drug in subjects suffering from this pathology. After a single subministration of the drug to the subjects suffering from Osteoporosis at a high turn-over, it has been considered as sensitive at the therapeutic effect. Subjects in whom, a lowering of the calcemia under 0.3 mEq/1 was obtained within ten hours since the drug had been given.