The studies dealing with bacterial findings of chronic maxillary sinusitis have been widely investigated in attempting to define the correct pathogens. The author performed bacteriological studies of nasal, nasopharyngeal and sinus discharge in 51 patients of chronic maxillary sinusitis to observe the relationship with each other and compared them with duration of illness, nasal septal deviation, nasal polyps associated with nasal allergy, nature of discharge, and histopathology of sinus mucosa. The results were as the followings ; 1) In 27 cases (52.9%) of nasal secretion, 14 cases (27.5%) of nasopharyngeal secretion and 26 cases (51.0%) of sinus secretion, some aerobic bacteria grew and most common bacteria were staphylococcus and K. pneumoniae in nasal and sinus secretion, and staphylococcus and E. aurogenes in nasopharyngeal secretion. 2) 11 cases were cultured in nasal and nasopharyngeal secretion, 16 cases in nasal and sinus secretion, 9 cases in nasopharyngeal and sinus secretion, and 8 cases in nasal, nasopharyngeal and sinus secretion. Among these, the isolation of same bacterial strains was 54.5%, 62.5%, 0% and 37.5% in the order. 3) In sinus secretion, 13 cases showed anaerobic bacteria in which peptostreptococcus was the most prevalent as 6 cases. Aerobic bacteria in each of three sites were not found in 17 cases of which 7 cases (41.1%) showed anaerobic bacteria in sinus secretion. 4) There was some tendency to increasing isolation of aerobic bacteria in relation to prolonged duration of illness. 5) The number of bacteria in the nasal and sinus secretion was prominent in the patients with nasal septal deviation and only those who had nasal polyps, polyps with nasal secretion. 6) Bacterial isolation rate was higher in purulent nasal and nasopharyngeal secretion, but lower in purulent sinus secretion than nonpurulent nature. 7) There was no characteristic correlation between histopathology of sinus mucosa and bacterial isolation.