Malignant fibrous histiocytoma is a new malignant tumor entity of histiocytic origin which arises as a primary tuor of the bone as well as the soft tissue. Radiologic features of 12 cases of pathologically proven intra-and extraosseous malignant fibrous histiocytoma were analyzed. RESULTS : 1. Seven cases were of soft tissue origin and 5 cases were of primary bone origin. 2. Seven were male and 5 were female : Eight cases were beyond 5th decades.3. The clinical presentations of malignant fibrous gistiocytoma of the soft tissue origin were a mass with rapid growth or high rate of local recurrence. The roentgen evidence of soft tissue density mass was demonstrated in 7 cases and scintigraphic evidence of cortical invasion was suggested in 2 cases. 4. Malignant fibrous histiocytoma arising fro bones had ill defined moth-eaten osteolytic lesion with cortical destruction, periosteal reaction and soft tissue extension. 5. Among 12 cases, there were 2 cass of pulmonary metastases and 2 cases of osseeous metastases. 6. In the presence of soft tissue mass with locally aggressive behavior and/or nonspecific roentgen features of malignant bone tumor, one should consider the possibility of malignant fibrous histiocytoma.