To study the bacterial flora in the upper respiratory tract we examined bacteria obtained from the larynx, posterior pharyngeal wall, palatine tonsil and nasal cavity to identify the constitutent strains and check for the existence of beta-lactamase in 37 subjects without infectious otolaryngological disease who underwent surgery with general anesthesia. A tendency toward a decrease with aging in aerobes and an increase in anaerobes was observed. The influence of fibronectin was considered to be one of the reasons for this tendency. beta-lactamase production strains showed a tendency to increase in the age group from 20-49 years and decrease in subjects 50 years and older. The number of constitutent strains in the nasal cavity was less than that in the pharynx, which was considered the result of the mucociliary function as a biophylactic function. Comparing the constitutent strain types in the larynx with those in other areas, the posterior pharyngeal wall showed the highest coincident rate of 70%, Notably, the coincident rate was more than 80% among aerobes. This suggests that causative bacteria can be estimated from pharyngeal culture.