This multicenter, noncomparative, nonrandomized study evaluated the clinical efficacy and safety of ceftriaxone for treating acute otitis media in children following clinical failure of oral antibiotic therapy. Middle-ear fluid samples were collected on day 0 and on day 3, 4, or 5 (day 3 to 5) and were used to test whether ceftriaxone therapy can eradicate Streptococcus pneumoniae isolates with increased resistance to penicillin (MIC  1 mg/liter). At the first visit, on day 0, middle-ear fluid was sampled for bacteriological testing by tympanocentesis or otorrhea pus suction. Patients were administered 50 mg of ceftriaxone/kg of body weight/day, injected intramuscularly once daily, for 3 days. A second sample was collected by tympanocentesis if a pneumococcus isolate for which the MIC of penicillin was 1 mg/liter was detected in the day-0 sample and if the middle-ear effusion persisted on day 3 to 5. This second sample was tested for bacterial eradication. One hundred eighty-six children aged 5 months to 5 years, 10 months, with acute otitis media clinical failure were enrolled and treated in this trial. On day 10 to 12, 145 (83.8%) of the 173 patients evaluable for clinical efficacy were clinically cured. Of the 59 patients infected by pneumococci, 36 had isolates for which the MICs of penicillin were 1 mg/liter. Of those patients, on day 10 to 12, 32 (88.9%) were clinically cured. Middle-ear fluid samples collected by day 3 to 5 following the onset of treatment with ceftriaxone were sterile for 24 of the 27 (88.9%) patients who were infected as of day 0 by pneumococci for which the MICs of penicillin were 1 mg/liter and who were evaluable for bacteriological eradication. On day 10 to 12, 81.4% of S. pneumoniae-infected children and 87.5% of Haemophilus influenzae-infected children were clinically cured. No discontinuation of treatment due to adverse events, particularly due to local reactions at the injection site, were reported. Only 11 adverse events which had doubtful, probable, or possible links with the study treatment were recorded. Both the bacteriologically assessed eradication of pneumococci for which the MICs of penicillin were 1 mg/liter and the clinical cure rates demonstrate that ceftriaxone is of value in the management of acute otitis media unresponsive to previous oral antibiotic therapy.