Lethal midline granuloma (L.M.G.) is a rare disease characterized by ulceration and rapid destruction of upper respiratory tract including the nose, nasopharynx, palate, paranasal sinus and midface. According to Kassel's classification (1972), lethal midline granuloma falls into distinct and seperate clinicopathological entites, 1) malignant lymphoma 2) midline malignant reticulosis, and 3) Wegener's granulomatosis. Midline malignant reticulosis is a neoplastic process characterized by pleomorphic lymphoreticular cell infiltration pathologically identical to a lymphoreticular malignancy. Authors experienced 6 cases of lethal midline granloma during past 3 years. Five of them were midline malignant retculosis and the other one was Wegener's granulomatosis.