Hemangioendotheliosarcoma in the region of the head and neck was a very rare, highly malignant and poorly prognostic tumor. The authors experienced recently a case of hemangioendotheliosarcoma involving the right maxillary sinus. A 17-year-old boy was admitted on Sept. 21 1977, with the complaints of tenderness and swelling of right cheek which had developed gradually for two and a half months after blunt trauma on right cheek. Diagnostic antral irrigation revealed a large amount of old blood coagula and relatively poor ventilation. Radiological findings of the maxillary sinuses showed total hazziness, widening of the right maxillary sinus and bony destruction of the right orbital floor. On Sept. 23 1977, right side Caldwell-Luc's approach was done under local anesthesia, out complete removal of cystic tumor was impossible, because of adhesion of mass to the necrotic infraorbital and invaded to intraorbital cavity. Postoperative histopathological study confirmed hemangioendotheliosarcoma and recommended irradiation therapy.