In acute lung injury (ALI) by lipopolysaccharide (LPS), the underlying cause of infiltration and migration of neutrophils into the alveoli is considered to be from increased production of platelet-activating factor (PAF) in the pulmonary surfactant lining the alveolar lumen. In this study I partially confirmed this concept. LPS increased lung leak and the infiltration of neutrophils in the lung of rats given LPS intratracheally. The migration of neutrophils into the lung, which had caused oxidative stress, was also morphologically identified. I verified that the metabolism of the pulmonary surfactant was affected and that there was increased production of PAF in the pulmonary surfactant, both of which are considered to contribute to ALI by LPS in rats.