Ceftriaxone has greater in vitro and in vivo efficacy against many common bacteria than other third-generation cephalosporins. Single-dose ceftriaxone pharmacokinetics were studied in 17 patients, aged 0.6 to 52 months, with infections of the central nervous system. Patients received a randomized dose of 50 or 75 mg/kg ceftriaxone intravenously over 5 minutes on the second to fifth day of illness. Serial blood samples were collected over 24 hours in all patients, and cerebrospinal fluid (CSF) was obtained 1 to 4.5 hours after injection. Ceftriaxone mean peak plasma concentrations, determined by high-power liquid chromatography, were 267 and 184 microgram/ml for the 75 and 50 mg/kg dosage groups, respectively. The harmonic mean elimination half-life was 4.2 hours, and the mean percent drug penetrance into CSF was 4.8 +/- 3.5%. Of CSF studies evaluated, the glucose concentration was correlated most closely (inversely) with CSF penetration of ceftriaxone. Individual CSF concentrations of ceftriaxone exceeded the minimal inhibitory concentrations of the respective bacteria causing infection by 480 to 5,600 times. Ceftriaxone may be useful in the treatment of serious pediatric infections, including meningitis.