The patient was a 77-year-old man who noted swelling his left leg, and a left lower abdominal mass. Extended resection of the tumor was combined with resection of the externaliliac vein and replacement a synthetic graft. Histopathological diagnosis was malignant fibrous histiocytoma (MFH) of the myxpid type. The patient is alive and well with no local recurrence or metastasis 10 months after the operation. Sufficient flow inthe synthetic graft was identified by color flow duplex scanning. MFH is the most common among soft tissue sarcomas. An MFH arising in the retroperitoneum often invades other organs, and it is difficult to resect it entirely resulting in poor prognosis. Therefore we suggest that extended resection including resection of vessels with replacement is necessary for treatment of MFH.