Metastasis from a giant-cell tumor of bone that is histologically benign has become a recognized entity. To date, thirty-one pathologically proved cases have been reported in the world literature. To this, we add eight cases from our experience of more than 400 cases of histologically benign giant-cell tumor of bone. The lungs are the principal site of metastasis, the lesions being pathologically indistinguishable from the primary tumor. The metastatic process is unpredictable as to clinical aggressiveness, and the mortality rate is approximately 25 per cent. We advise aggressive attempts at complete extirpation of metastases.