The acute metabolic abnormalities associated with cancer may cause symptoms that require urgent medical treatment and may constitute a more dangerous threat to life than the cancer itself. Hypercalcaemia is probably the most common metabolic complication of neoplastic disease (occurring in up to 30% of cancer patients) and its timely treatment may often save the patient and may permit subsequent chemotherapy. In this communication we focused our attention on the pathogenetic mechanism (part 1), diagnosis and subsequent treatment of this metabolic disorder (part 2).