OBJECTIVE: To study the relationship between pathogenic bacteria in the nasal middle meatus and acute bacterial respiratory infection in children. METHODS: Three hundred and twenty eight children with respiratory infection (mean age 8 years) were included into the prospective cohort study. The mucosal fluid specimens from the nasal middle meatus were collected under an endoscope for bacterial culture. The patients with bacterial culture positive were defined as the Exposed group and those with bacterial culture negative as the Non-exposed group. The grouping of the patients was blinded to the patients, patients' parents and physicians. Both groups received anti-virus and symptomatic treatments, without antibiotic administration. Five days later, the patients were evaluated as to whether they had bacterial infection based on the leucocyte count and CRP results. RESULTS: Of the 328 patients, 168 had a positive nasal bacterial culture. The incidence of bacterial respiratory infection in the Exposed group [51.2% (86/168)] was significantly higher than in the Non-exposed group [ 13.1% (21/160)] (P<0.01). The relative risk of bacterial respiratory infection occurrence in patients with nasal bacterial culture positive was 3.9002. CONCLUSIONS: The children with respiratory infection who had potential pathogenic bacteria in the nasal middle meatus were more prone to develop bacterial respiratory infection.