SynopsisPorcine calcitonin was administered intramuscularly at doses of 4.5-10MRC u.per day to patients with metastatic bone carcinoma, osteoporosis and polyostotic fibrous dysplasia during 22-50 days period. Transient effects of calcitonin were also investigated in hypercalcemia of primary hyperparathyroidism, multiple myeloma and vitamin D intoxication.Serum calcium and/or magnesium showed gradual decrease during the period of administration in metastatic bone carcinoma, senile osteoporosis and polyostotic fibrous dysplasia. Urinary calcium and/or magnesium also decreased in metastatic bone carcinoma and osteoporosis. Alkaline phosphatase did not change during the period of calcitonin treatment but was lowered in the posttreatment period in polyostotic fibrous dysplasia. Serum hydroxyproline showed a transient decrease in metastatic bone carcinoma.Hypercalcemia of multiple myeloma and vitamin D intoxication was improved temporarily by calcitonin. These results suggest a beneficial effect of calcitonin in the treatment of some of the bone diseases and hypercalcemia.