A total of 33 patients with bacterial meningitis were treated with single daily doses of ceftriaxone (CTR 100 mg/kg/day i.v.) for a median duration of 13 days. Pathogens isolated by culture and/or determined by latex agglutination were 15 Haemophilus influenzae b, 7 Neisseria meningitidis, 2 Streptococcus pneumoniae, 1 group B streptococcus, 2 Streptococcus viridans and 2 Staphylococcus epidermidis. In 4 cases a diagnosis of purulent meningitis could only be made by means of the inflammatory liquor parameters. All cerebrospinal fluid (CSF) drug levels even at the end of the dosing interval were at least 10-fold higher than the MICs of the respective bacterial isolates. The average penetration of CTR into the CSF was 6.6%. Within 12-46 h after the first dose, control spinal taps were performed. Cultures were sterile in all cases. Side effects encountered were diarrhea, exanthema, neutropenia and transient elevation of glutamic oxaloacetic transaminase, but none caused a change of therapy. One patient developed a biliary concrement. No patient died; 5 patients had prolonged fever (greater than 5 days), and 2 were left with persistent hearing deficiencies. CTR can be recommended as a safe and effective antibiotic agent for once daily treatment of bacterial meningitis in children.