We have observed histopathologically the mucous membrane of the maxillary sinus in 60 cases that received caldwell-Luc's operation during the period from Jan. 1984 to July 1985 in Chosun University Hospital. The results were obtained as follows : 1) In sex distribution, 33 cases(55%) were males and 27 cases(45%) were females and the ratio between male & female was about 1.2 : 1. In age distribution, the highest incidence was noticed between 15-19 years of age(38 cases 63.3%). 2) The morphological classification of lining mucosa revealed as follows ; edematous type in 25 cases(41.7%), hypertrophic type in 24 cases(40%) and polypoid type in 11 cases(18.3%). The nature of retention fluid in maxillary antrum revealed as follows ; Purulent in 40 cases(66.7%), mucoid in 17 cases(28.3%) and serous in 3 cases(5%). 3) The pathological classification revealed as follows ; edematous type in 28 cases(46.7%), infiltrating type in 21 cases(35%) and fibrous type in 11 cases(18.3%). 4) The state of mucous gland revealed as follows ; marked hyperplasia in 10 cases(16.7%), moderate hyperplasia in 29 cases(48.3%) and normal or atrophy in 21 cases(35%). 5) The change of blood vessel revealed as follows ; marked change in 9 cases(15%), moderate change in 19(31.7%) and slight change in 32 cases(53.3%). 6) The degree of cell infiltration revealed as follows : marked infiltration in 16 cases(26.7%), moderate infiltration in 19 cases(31.7%) and slight infiltration in 25 cases(41.6%).