The authors report five cases of malignant fibrous histiocytoma of the soft tissues, some of them with atypical presentation (necrotizing tumor, hypereosinophilic syndrome, dermatomyositis). This is the first case of polymyositis associated with malignant fibrous histiocytoma. The tumor occurs between the fifth and the seventh decade, principally as a mass on the proximal lower limb. Local recurrence and metastasis occurs in 50% of patients. Prognosis is dependent on both the surgical possibilities and the characteristics of the tumor (site, size, histologic grade). Surgery alone is inadequate. Adjuvant chemotherapy improves the 5-year survival.