Lipopolysaccharide plays a major role in the development of lung injury induced by gram-negative bacteria, but a protective agent to attenuate the LPS-induced lung injury has not been found. The aim of the studies was to examine the effect of neutrophil elastase specific inhibitor or niacin on LPS-induced acute lung injury. We administered LPS (Escherichia coli) 0.1 mg/kg body weight, transtracheally into the lungs of hamsters. Either neutrophil elastase specific inhibitor or niacin was injected intraperitoneally before and after the LPS administration. Animals were sacrificed 24 h later and the wet-to-dry lung weight ratio (W/D) was determined. Bronchoalveolar lavage (BAL) was performed, and tissue sections were examined histologically. LPS treatment increased W/D, albumin content and neutrophil counts in BAL. In hamsters treated with elastase inhibitor or niacin, W/D, albumin content and intra-alveolar inflammatory cell infiltration were normal. We conclude that neutrophil elastase inhibitor and niacin attenuates LPS-induced acute lung injury.