A clinicopathologic study of 130 cases of malignant fibrous histiocytoma (MFH) of the soft tissues is reported. This malignant neoplasm principally of middle and late adults occurred most often in the proximal portions of the extremities (48%) including the thigh and buttocks (35%). MFH may be subclassified into common (storiform and pleomorphic), myxoid, xanthogranu-lomatous, and giant cell types, the common type being accounted for 100 cases (77%) of the series. The prognosis was more favorable in patients with storiform and myxoid tumors than in patients with pleomorphic or other type tumors, the overall relative five-year survival rate being 48%. The depth of the tumor also affected prognosis with a significantly lower survival rate in deeply situated tumors. The rate of local recurrence of the tumor was 48%. Because of incomplete informations, metastasis was confirmed in only 26 patients and was most frequently to the lung (73%). In addition, electron microscopic, histochemical and tissue culture findings in limited cases are presented, concerning the histogenesis of the MFH.