The variability in causative organisms of the chronic maxillary sinusitis might be due to differences in the environment, economical status, techniques of transportation of specimens, cultivation of organisms, but recently resistant strains and mixed infections were increased due to antibiotic abuse. The clinicobacteriological study was carried out on 96 patients(114 sinuses) with chronic maxillary sinusitis who received Caldwell-Luc's operation at Department of Otolaryngology, Chunan Hospital, College of Medicine. Soonchunhyang University during 2 years from Jan. 1988 to Dec. 1989. The following results were obtained；1) Disease duration was most common in 1-5 years(61 patients. 63.5%), and organisms were isolated 84 patients(87.5%), 98 sinuses(86.0%) and were not grown from 12 patients(12.5%), 16 sinuses(14.0%). 2) Among isolated strains, Streptococcus was most common in 59 sinuses(51.1%), Staphylococcus 50 sinuses(43.9%) in order. 3) In general, isolated organisms were sensitive to Cephalosporin, Ampicillin, Erythromycin and Streptococcus was sensitive to Cephalosporin, Ampicillin, Penicillin, Erythromycin and Staphylococcus was sensitive to Cephalosporin, Methicillin, Amikin, Tobramycin. 4) In general, isolated organisms were resistant to Tobramycin, Gentamicin, Amikin and Streptococcus was resistant to Tobramycin, Amikin, Gentamicin, Methicillin and Staphylococcus was resistant to Terramycin, Gentamicin, Penicillin.