The intravenous administration of Clodronate, a strong inhibitor of osteoclastic activity provides a safe and very effective treatment of hypercalcemia whether secondary to bone metastasis or due to paraneoplastic syndrome. Its action is fast, exclusively osseous and lasts up to 7 days. The response is incomplete when increased renal absorption is the predominant mechanism of hypercalcemia. The data published by Elomaa et al on osteolytic metastases in breast cancer patients show a significant improvement with regard to pain reduction, prevention of fractures as well as hypercalcemia. The results obtained using a 1-yr oral treatment need further confirmation.