CONCLUSIONS Bacterial predominance and antibiotic sensitivity have changed over time, making continuous and periodic surveillance necessary in guiding appropriate antibacterial therapy. OBJECTIVE With the development and widespread use of antibiotics, the types of pathogenic microorganisms and their resistance to antibiotics have changed. Knowledge of the species and resistance rates of current pathogens is important for determining the appropriate antibiotics for patients with chronic suppurative otitis media. We investigated the current bacteriology of chronic suppurative otitis media. METHODS This was a retrospective study of 1102 patients with chronic suppurative otitis media seen at six hospitals in Korea from January 2001 to December 2005. RESULTS The most commonly identified pathogenic bacterial species was Pseudomonas, with the next most prevalent being methicillin-resistant Staphylococcus aureus (MRSA).