This retrospective study of 407 cases of giant cell tumor indicated that most tumors were in the expected locations, usually in the end of a major tubular bone. Female patients accounted for a definite, but slight, majority. Five patients had metaphyseal tumors, and three patients had multifocal tumors. Only one tumor occurred in a lesion of Paget disease. Local soft-tissue implantation, ordinarily with the implant having a mineralized shell, was observed in 10 of the cases. Eight patients had tumors that produced benign metastatic lesions, and two of them have died. Histologically, malignant change developed in 28 of the cases; in 21 of these, radiation had been included in the treatment of the primary lesion.