The aim of this work was to assess the commensal flora in the adult middle meatus. Thus, 139 samples were taken from subjects of both sexes, over 16 years of age, seen in the community or hospitalized for less than 72 hours for non-rhinological conditions. They had had no nasal or sinus conditions in the previous three months. One hundred and thirteen samples contained at least one aerobic or anaerobic bacterium. Fifty-nine samples yielded a single organism in culture. A maximum of five organisms were isolated from a given patient. These results show that the adult middle meatus contains a mixed commensal flora and should prove useful in interpreting endonasal swab cultures during acute and chronic sinus infection.