The effect of aerobic bacteriology on the clinical presentation, complications of the disease and long-term results of surgical treatment was assessed in a cohort of 368 patients with chronic suppurative otitis media. Bacteriological findings showed no significant difference between child and adult patients. Staphylococcus aureus was isolated in cholesteatoma ears more frequently than Pseudomonas aeruginosa, in chronic ears without cholesteatoma the situation was reversed. Bacteriological findings had no significant effect on the incidence of complications caused by the disease. Failures after surgical treatment were most common in Pseudomonas ears. The bacteriology had no significant effect on pre-operative hearing levels nor postoperative hearing results. It was concluded that, in order to improve results of chronic ear sugery, more attention should be paid to pre-operative conservative treatment of chronically discharging ears, especially those infected by P. aeruginosa.