This study was undertaken to clarify the effects of urinary trypsin inhibitor (UTI) on lipopolysaccharide (LPS)-induced acute lung injury. Rabbits were randomly assigned to one of seven groups: saline only, UTI, LPS, pre- or post-UTI-high (infusion of UTI of 25,000 U/kg followed by 25,000 U/kg over 2 h), pre- or post-UTI-low (infusion of UTI of 2,500 U/kg followed by 2,500 U/kg over 2 h). UTI was administered 30 min before (pre-groups) or 15 min after (post-groups) LPS administration. Rabbits were mechanically ventilated with 40% oxygen for 6 h. LPS decreased peripheral blood leukocyte counts and increased wet/dry weight ratio of lung, lung injury score, neutrophil infiltration in lung, and IL-8 production in systemic blood and bronchoalveolar lavage fluid (BALF). Rabbits treated by UTI were protected from LPS-induced lung injury, as determined by wet/dry weight ratio, neutrophil infiltration in lung, lung injury score, and IL-8 in BALF levels. UTI attenuated LPS-induced acute lung injury in rabbits mainly by inhibiting neutrophil and IL-8 responses, which may play a central role in sepsis-related lung injury.