Abstract Aggressive central giant cell granulomas may be eliminated by administering human calcitonin 0.5 mg (100 iu) deep subcutaneously for 1 year. This avoids the need for mutilating surgery or radiotherapy in growing children. Aggressive recurrent peripheral lesions (the giant cell epulis) can also be treated by excision after calcitonin therapy. These giant cell granulomas should be redefined as osteoclast granulomas, and the aneurysmal bone cyst, the cystic osteoclast granuloma. However the stimulus for the disturbance in the osteo progenitor spindle cell needs to be defined.