An organism must maintain a fairly constant balance of pH to survive. Most bacteria grow the best in a narrow range of pH from 6.5 to 7.5. Ninety-six patients with chronic suppurative otitis media were selected. Two weeks before the treatment they were instructed to stop taking any antibiotics; then a sterile swab culture was taken from auditory canal secretions and at the same time the pH of the secretions were measured. Otomicroscopic examination of the ear with cleaning of purulent debris was done. All patients received ear irrigation with 2% acetic acid solution three times per week for the maximum of 3 weeks without antibiotic therapy. Any patients with cholesteatoma, polyp, granulation and otomycosis were excluded. Patients were followed for up to 3 years. Fifty-five patients (57%) had resolution of their original otorrhen, whereas 19 patients (20%) developed healed ear drum perforation. The remaining 14 patients (15%) showed recurrence and 8 of them (8%) had no response to the treatment.