Malignant fibrous histiocytoma (MFG) is a rare bone tumor occuring 10 times less frequently than osteogenic sarcoma. secondary sarcomatous transformation has been reported in association with infarction of bone6,7,8), irradiation4), infectoin3), and trauma1,5). We report a case of a patient in whom malignant fibrous histiocytoma developed in an area adjacent to a infected non united fracture of the tibia at seven months after the fracture. There was no clinical or radiographic evidence of pre-existing neoplasia.