We evaluated the diffusion of cefpirome into the cerebrospinal fluid (CSF) of 25 patients with bacterial meningitis or ventriculitis who were receiving conventional antibiotic treatment. A single cefpirome dose of 2 g was infused at day 2-3 after the onset of therapy. Concentrations of cefpirome in serum and CSF obtained at 2, 4, 8 or 12 h after the infusion were determined by high-performance liquid chromatography. The mean (+/- S.E.M.) concentrations of cefpirome in CSF ranged from 2.26 +/- 1.16 to 4.17 +/- 0.83 mg/L. These concentrations were higher than the MBCs for the pathogens usually responsible for bacterial meningitis.