Fifty-four patients with active chronic suppurative otitis media (CSOM) were prospectively studied for the bacteriology and their in vitro antibiotic susceptibility to ofloxacin. Thirty-nine patients (72%) had positive cultures. The commonest organism was Pseudomonas sp., which was found in 18 (33%) patients. The second commonest organism was Staphylococcus aureus, which was found in 15 (28%) patients. Bacteroides sp. was found only in 3 (6%) patients, and all were in association with the aerobes. Of all 42 aerobes found, 35 (83%) were susceptible to ofloxacin. The in vitro susceptibility results indicate that ofloxacin can be an effective antibiotic in the treatment of active CSOM.