The aerobic microorganisms present in 51 middle ears of 36 children with chronic suppurative otitis media without cholesteatoma were evaluated. Specimens were taken directly from the middle ear through a patent perforation or tympanostomy tube and cultured using standard techniques. Twenty-three microbiologic species were identified, with Pseudomonas aeruginosa being the most prevalent (67% of ears) and the only organism in 31% of ears. The initial treatment of all patients was intravenous administration of an antimicrobial selected on the basis of culture and susceptibility reports; this treatment was successful in all but four children, who subsequently required tympanomastoid surgery. These results indicate that medical therapy, based on the results of culture and susceptibility studies, provides a viable alternative to major mastoid surgery in the management of chronic suppurative otitis media without cholesteatoma.