The lesion showing progressive, locally invasive, destructive inflammatory process in the nose, paranasal sinus, palate or other upper aerodigestive tract has been known as a lethal midline granuloma and most clinicians still use it. But this term is defined clinically, and most pathologists disagree with it. Histopathological differentiation is so difficult as to decide the therapeutic manner and to predict the prognosis. The authors carried out clinical observation on the 11 cases of so called midline granuloma syndrome diagnosed clinically or histopathologically. Four cases confirmed histopathologically as midline malignant reticulosis were treated with deep local irradiation therapy and the results were very fair.