Acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) are common syndromes that affect both clinical and surgical patients. This study describes the effects of a potent and specific N-methyl-d-aspartate receptor antagonist (MK-801) against oxidative stress in acute lung injury induced by intratracheal lipopolysaccharide (LPS) injection. This study was performed using male Wistar rats weighing 200-250g. Rats were randomly divided into four groups: control with isotonic saline instillation (n=6); LPS (100μg/100g of body weight) treated with saline (n=6); LPS treated with MK-801 (0.3mg/kg, intraperitoneally; n=6); LPS treated with MK-801 (0.3mg/kg, intratracheally; n=6). Twelve hours after the LPS instillation, rats were anesthetized and a bronchoalveolar lavage (BAL) was performed in order to determine the alveolar-capillary membrane alterations and the inflammatory infiltrate level. Blood and lung samples were isolated and assayed for oxidative stress variables and histopathologic analysis. The use of MK-801 decreased bronchoalveolar lavage fluid protein, LDH activity and inflammatory cells. Indeed, the treatment with MK-801 significantly attenuated lung oxidative damage and histopathologic alterations after LPS instillation. Our data provide the first experimental demonstration that MK-801 decreases oxidative stress and limits inflammatory response and alveolar disarray in lipopolysaccharide-induced acute lung injury.