Otitis media is the most common respiratory tract infection of infancy and early childhood that is managed with antibacterial agents. A bacterial pathogen is isolated from the middle ear fluids of approximately two-thirds of children with acute otitis media; S. pneumoniae is the leading bacterial pathogen followed by nontypable strains of H. influenzae and M. catarrhalis. Clearance of bacteria from middle ear fluid without use of antibacterial drugs is evident in studies in which a placebo is used. Whereas pneumococci continued to be isolated from middle ear fluids when the infection was not treated, approximately one-half of infections due to nontypable H. influenzae and up to 80% of those due to M. catarrhalis cleared. The microbiological data suggest that only one-third of patients with acute otitis media require antibacterial therapy for resolution of clinical signs and symptoms. However, without the results of prior tympanocentesis, the physician cannot identify the patients for whom the infection will resolve. Thus, the data support use of antibacterial agents for all episodes of acute otitis media to cover adequately the one-third of children who will need the antimicrobial agent to recover from the infection. Effusion persists in the middle ear for weeks to months after every episode of acute otitis media. Conductive hearing loss of some degree occurs whenever the middle ear space is filled with effusion. Decreased scores in tests of speech and cognitive abilities for infants and children who had prolonged middle ear effusion has stimulated investigators to seek means to reduce the duration of middle ear effusion following acute otitis media. Because the pathogenesis of persistent middle ear effusion is uncertain, the results with medical therapies, including antibiotics and steroids, have been inconsistent. Placement of ventilating or tympanostomy tubes to produce drainage and ventilation of the middle ear and to restore hearing is effective and is now the second most frequent surgical procedure in children (after circumcision), but the criteria for placement of tubes are controversial. Prevention of otitis media is possible by use of chemoprophylaxis or vaccines. Chemoprophylaxis has been effective in children with recurrent acute otitis media by reducing new episodes by 40%-90%. A serum antibody response that is age- and type-specific follows pneumococcal infection and protects against subsequent homotypic infection. Polysaccharide pneumococcal vaccines are not consistently immunogenic in children > 2 years of age, but experimental conjugate polysaccharide vaccines are immunogenic in infants as young as 2 months.(ABSTRACT TRUNCATED AT 400 WORDS)