The data obtained from 114 case histories of giant cell tumor were analysed on the EC-1010 type computer to identify clinico-roentgenological factors influencing the frequency of relapse and metastasis development. Such factors as tumor localization in tibia, local lesions in the abnormally thin cortical layer detectable by X-ray examination, the lytic form of tumor and tumor excochleation proved to be unfavorable. In the analysis of cases of metastatic spread, information could be acquired only from roentgenologic characteristics which permitted complete decay of the cortical layer, the presence of soft-tissue component in tumor and pathologic fracture to be identified as manifestations of caries.