We reviewed the cases of seven patients with histologically benign primary giant-cell tumor of bone and histologically proved metastases to the lung. All seven had a Stage-3, aggressive, benign lesion with interruption of the cortex and soft-tissue extension. The main histological features of the primary lesion were identical to those of the pulmonary metastases. In only one of the seven patients were the metastases detected simultaneously with the primary lesion. All seven patients were treated by surgical resection of the lung nodules and chemotherapy. Of the seven patients, four were alive and free of disease after an average follow-up of nine years; two were receiving chemotherapy; and one, who had had immunosuppression for an allograft transplant, died less than one year after the discovery of the pulmonary lesions. Based on this small series, we concluded that patients with a Stage-3 giant-cell tumor of bone may be at risk for pulmonary spread of the disease. This lesion, with its benign histological picture even in lung lesions, has a favorable prognosis when treated with pulmonary resection of the nodules. However, the role for chemotherapy after pulmonary surgery is still unclear.