A case of malignant fibrous histiocytoma arising primarily in the left maxillary sinus is described. The patient, a 39‐year‐old male, who had suffered from sinusitis for 20 years, began to have paresthesia or sharp pain of the left side of the face and toothaches of the left maxilla. At operation a white fibrous tumor developing extensively from the lateral wall to the upper and medial walls of the left maxillary sinus and into the ethmoidal sinus was noted. Following gradual progression of dyspnea, he died approximately one year after the onset in spite of radiation therapy and anticancer chemotherapy. An autopsy revealed recurrence of the tumor in the left maxillary sinus with wide‐spread metastases to the lungs, pleurae, pancreas, kidneys and bone marrows. The direct cause of death was respiratory failure due to extensive growths of the pulmonary and pleural metas