BACKGROUND: Use of aspirin (acetylsalicylic acid [ASA]) was found to improve outcome in animal models of acute lung injury (ALI) or its more severe form, acute respiratory distress syndrome. In patients with acute respiratory distress syndrome, data indicating a protective effect of ASA are less convincing. We hypothesize that ASA in a high dose is superior to low-dose ASA in preventing lung injury. Also, the effect on lung injury of inhibiting platelet activation by clopidogrel was investigated. METHODS: Acute lung injury was induced by intranasal instillation of 10 μg lipopolysaccharide (LPS). Before LPS, BALB/c mice were pretreated with either high dose of ASA (100 μg/g intraperitoneally, low-dose ASA (12.5 μg/g i.p), clopidogrel (50 μg/g i.p), or clopidogrel in combination with low dose of ASA. Controls received vehicle or LPS without intervention. Five hours after LPS, bronchoalveolar lavage fluid (BALF) and plasma were obtained. MEASUREMENTS AND MAIN RESULTS: All treatment regimens reduced neutrophil influx in the BALF compared with LPS controls (high-dose ASA 75% ± 2% [mean ± SD], low-dose ASA 86% ± 3%, clopidogrel 82% ± 1%, and low-dose ASA-clopidogrel 82% ± 3% vs. LPS control 88% ± 2%; P ≤ 0.05). High-dose ASA reduced BALF levels of protein compared with LPS controls (median [interquartile range], 0.2  vs. 75  pg/mL; P < 0.01), to a greater extent than after low-dose ASA (48  pg/mL), clopidogrel (37  pg/mL), or low-dose ASA-clopidogrel (57  pg/mL). CONCLUSIONS: High-dose ASA is superior to low-dose ASA, clopidogrel, and to a combination of clopidogrel and low-dose ASA in attenuating LPS-induced lung injury in mice, suggesting high-dose ASA to be the antiplatelet therapy of choice in further research on preventing ALI.