I have observed histopathologically the mucous membrane of the maxillary sinus and ipsilateral inferior and middle nasal turbinates in thirty the random cases (18 patients) who received Cald-well Luc's operation during the period from January through October, 1971 in National Medical Center. The results are as follows : 1) The mucous membrane of the inferior turbinate revealed mostly a edematous change (66.0%) in chronic paranasal sinusitis of the edematous type and a fibrous changes (71.4%) in that of the fibrous type. 2) The changes of the middle turbinate was similar to that of the inferior turbinate. 3) The edematous changes of the mucous membrane was seen more frequently in the sinus membrane (60.0%) than in the turbinal membrane (inf. 46.7%, mid. 43.3%). 4) Pus, or muco-purulent accumulation (88.8%) in the sinus cavity were found more frequently in the cases of edematous changes of the sinus mucous membrance and mucoid (80.0%) in that of infiltrative changes. 5) I assume that the changes of the mucous membrane of the sinus having some relation to pneumatization of the sinus. The mucous membrane of the sinus revealed mostly a edematous changes (76.9%) in the pneumatic type and fibrous changes (57.1%) in that of the sclerotic type. 6) No specific relationships were found among cell infiltration, mucus gland and vascular changes of the mucous membrane of the sinus and turbinates and types of the membrane.