Malignant fibrous histiocytama is currently defined as a malignant primary bone tumor, and that may contain fibromatoua, xanthomatous, or histiocytic elementa, varing widely in the degree of anaplasia that is present. The principal lesions to be considered in the differential diagnoais of malignant fibrous histiocytoma are osteogenic sarcoma and fibrosarcoma. Malignant fibrous histiocytoma is more sensitive to chemotherapeutic ageata than are osteosarcama and fibrosarcama. In this paper 2 cases sre reported, including the one in which the tumor arose in a midahaft of the femur and the other one arosein the upper metaphyseal portion of the tibla.