Polymorphic reticulosis is characterized by relentlessly progressive, localized, destructive inflammatory process that predominantly involves upper respiratory tract, nose, paranasal sinues, nasopharynx and face. It has been called many terms because of variable histopathological finding. The diagnosis of polymorphic reticulosis is rather difficult and confused with Wegener's granulomatosis and malignant lymphoma but histologic differenciation is feasible. Recently the authors carried out clinical observation on the 5 cases of polymorphic reticulosis diagnosed histopathologically after repeated biopsy and treated by radiation therapy with good results. The obtained result were as follows ; 1) The male and female ratio were 2 : 3. 2) 5 cases fell into the ages from 29 to 55 years and mean age was 45.2 years. 3) The primary lesion of the diseases were 3 cases of nasal cavity, only, one case of nasal cavity, nasopharynx and soft palate, one case of pharynx and epiglottis. 4) The results of biopsy was different in each biopsies. The final diagnosis performed twice of even four times of biopsy. 5) All cases were treated by radiation with dosage from 3,500 to 5,500 rads and results of treatment were favorable and all patients are alive at 1 to 5 years on follow-up.