5 patients of midline malignant reticulosis were treated by radiation therapy during the period from Feb., 1984 to Oct., 1984 at the department of therapeutic radiology, Inje medical College, Seoul Paik Hospital. 4 patient were male and 1 patient was female. Ages ranged from 30 to 87 years. After 1 year follow up, 4 patients survived; 3 patients without recurrent disease and I patient with disease, and 1 patient died of the disease. Midline malignant reticulosis is rare in occurrence. Still its definition and pathologic features are nat well established. Radiation therapy has long been known to be an effective treatment in localized disease. In the preaent paper we provide 5 cases of midline malignant reticulosis to discuss their pathologic findings and therapeutic results.