This study evaluates the ability of the new fluoroquinolone trovafloxacin to attenuate the inflammatory burst known to occur after initiation of antibiotic treatment in pneumococcal meningitis. After exposure to trovafloxacin or ceftriaxone for 3 h in vitro, Streptococcus pneumoniae was injected intracisternally (i.c.) into rabbits every 3 h over 9 h (n = 6 for each antibiotic). Ceftriaxone-treated S. pneumoniae induced consistently higher CSF leucocyte counts (median 2568/microL versus 543/microL at 6 h; P = 0.03; 4560/microL versus 2207/microL at 18 h; P = 0.03) than trovafloxacin-treated bacteria. Meningitis induced in rabbits by i.c. injection of live S. pneumoniae was treated with equal doses of trovafloxacin or ceftriaxone i.v. (ten per group). The bactericidal rates of both antibacterial agents in CSF were almost identical. In comparison with ceftriaxone, trovafloxacin resulted in lower tumour necrosis factor (TNF) and interleukin 1beta (IL-1beta) CSF levels 2 h after the initiation of treatment (TNF levels, median 26 U/mL versus 141 U/mL; P = 0.02; IL-1beta levels 455 pg/mL versus 1399 pg/mL; P = 0.02). Twelve hours after initiation of therapy, however, TNF and IL-1beta were higher in trovafloxacin-treated animals (TNF, 61 U/mL versus 7 U/mL; P = 0.001; IL-1beta, 4320 pg/mL versus 427 pg/mL; P = 0.006). The increase in CSF lactate was less during trovafloxacin therapy than with ceftriaxone (median: 2.0 mmol/L versus 4.0 mmol/L; P = 0.03). In conclusion, S. pneumoniae treated in vitro with trovafloxacin induced less CSF leucocytosis than ceftriaxone-treated S. pneumoniae. After i.c. inoculation of live S. pneumoniae, trovafloxacin therapy delayed, but did not inhibit, the release of the proinflammatory cytokines TNF and IL-1beta, probably by slowing the liberation of bacterial cell wall components into the subarachnoid space.