Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are associated with high rates of morbidity and mortality. Currently, several surfactant or anti-inflammatory drugs are under test as treatments for ALI. Sodium aescinate (SA) has been shown to exert anti-inflammatory and antiedematous effects. In the present work, the authors explored the effects of SA and the possible mechanisms of SA action in rats with ALI induced by oleic acid (OA) administration. Eight groups of rats received infusions of normal saline (NS) or OA. Rats exposed to OA were pretreated with 1 mg/kg of SA, or posttreated with SA at low (1 mg/kg), medium (2 mg/kg), or high (6 mg/kg) dose; a positive-control group received methylprednisolone. The pressure of oxygen in arterial blood (P(O(2))) levels, the pulmonary wet/dry weight (W/D) ratios, and indices of quantitative assessment (IQA) of histological lung injury were obtained 2 or 6 hours after OA injection (0.1 mL/kg, intravenously). The levels of superoxide dismutase (SOD), malondialdehyde (MDA), matrix metalloproteinase gelatinase B (MMP-9), and tissue inhibitor of metalloproteinase (TIMP-1) in both plasma and lung tissue were also determined. Both pre- and posttreatment with SA improved OA-induced pulmonary injury, increased P(O(2)) and SOD values, lowered IQA scores, and decreased the lung W/D ratio and MDA and MMP-9 levels in plasma and lung tissue. SA appeared to abrogate OA-induced ALI by modulating the levels of SOD, MDA, and MMP-9 in plasma and lung tissue.