The aim of the present study is to study the pharmacokinetics in plasma, lung lymph and bronchial washing fluid after intravenous infusion of grepafloxacin (GPFX), in comparison with those of levofloxacin (LVFX). Four conscious sheep with chronically instrumented lung lymph fistulas and tracheotomy were prepared. GPFX and LVFX concentrations in plasma and lung lymph after intravenous infusion of the drugs (10 mg/kg) for over 10 min were measured. In addition serial bronchial washing with 50 mL normal saline was performed to obtain epithelial lining fluid (ELF) at 2, 4, 6, 8, 12, 24 h after the intravenous administration. The time courses of lung lymph concentration were almost identical to those of the concomitant levels of both GPFX and LVFX in plasma, suggesting that both GPFX and LVFX could be easily moved from plasma to pulmonary interstitium and/or lung lymph circulation. However, GPFX concentrations of ELF were significantly higher than LVFX concentrations over time after the administration. In addition, intracellular concentrations in ELF of GPFX were also extremely high compared with those of LVFX. These results demonstrated that penetration of GPFX in bronchial wall, bronchial epithelium and/or phagocytic cells was superior to that of LVFX. These observations suggest that the pharmacokinetic characteristics of GPFX in the lung may provide a new insight into the strategy for clinical treatment of various pulmonary infections, especially cytotropic bacterial infections.