The purpose of the study was to assess the bactericidal effects of a single oral dose of levofloxacin (LVFX) by examining the concentration of LVFX in alveolar epithelial lining fluid (ELF) from patients with lower respiratory tract infections (LRTI). Forty patients with LRTI took 500 mg of LVFX and then received a fiberoptic bronchoscopic procedure randomly 1, 4, 8, 12, or 24 hours following dosing. Bronchoalveolar lavage fluid and blood were collected at the time of the bronchopulmonary procedure, and the LVFX concentration was determined. The mean peak concentrations of LVFX in plasma and ELF were achieved at 1.5 hours (4.07 mg/L) and 1 hour (3.44 mg/L), respectively. The AUC(24h) samples were 50.12 mg . h/L and 34.51 mg . h/L, respectively. The permeability of LVFX, which was estimated based on the ratio of LVFX concentration in tissue fluids to that in plasma, was 0.78 on average across all time points. After a single dose of LVFX in patients with LRTI, the drug rapidly distributed into bronchopulmonary tissue, thereby suggesting this dose is capable of achieving the concentration in target organs required for bactericidal efficacy.