Gallium nitrate, a novel drug for the treatment of cancer-related hypercalcaemia, inhibits osteoclast activity but does not affect osteoclast morphology or viability. Limited clinical experience in patients with cancer-related hypercalcaemia indicates that gallium nitrate is effective in restoring normocalcaemia in 75 to 85% of patients and is well tolerated in those with preserved renal function, producing few clinically relevant adverse effects. In comparative clinical trials it proved a more effective antihypercalcaemic agent than calcitonin or etidronate and produced a longer lasting normocalcaemic response. Gallium nitrate would appear to be indicated in symptomatic patients with cancer-related hypercalcaemia who have failed to respond to adequate rehydration.