Background Valproic acid (VPA) improves early survival and organ function in a highly lethal poly-trauma and hemorrhagic shock model or other severe insults. We assessed whether VPA could improve organ function in a rat model of septic shock and illustrated the possible mechanisms. Methods Forty Sprague-Dawley rats were randomly assigned to four groups (n=10): control group, VPA group, LPS group, and LPS+VPA group. Lipopolysaccharide (LPS) (10 mg/kg) was injected intravenously to replicate the experimental model of septic shock. Rats were treated with VPA (300 mg/kg, i.v.) or saline. Six hours after LPS injection, blood was sampled for gas analysis, measurement of serum alanine aminotransferase, aspartate aminotransferase, urine nitrogen, creatinine and tumor necrosis factor-alpha. Lung, liver and kidney were collected for histopathological assessment. In addition, myeloperoxidase activity and tumor necrosis factor-alpha in pulmonary tissue were measured. Acetylation of histone H3 in lung was also evaluated by Western blotting. Results LPS resulted in a significant decrease in PaO2, which was increased by VPA administration followed LPS injection. In addition, LPS also induced an increase in the serum levels of alanine aminotransferase, aspartate aminotransferase, urine nitrogen, creatinine, and tumor necrosis factor-alpha. However, these increases were attenuated in the LPS+VPA group. The lungs, liver and kidneys from the LPS group were significantly damaged compared with the control group. However, the damage was attenuated in the LPS+VPA group. Myeloperoxidase activity and tumor necrosis factor-alpha levels in pulmonary tissue increased significantly in the LPS group compared with the control group. These increases were significantly inhibited in the LPS+VPA group. Acetylation of histone H3 in lung tissue in the LPS group was inhibited compared with the control. However, the level of acetylation of histone H3 in the LPS+VPA group was markedly elevated in contrast to the LPS group. Conclusions Treatment with VPA can attenuate multiple organ damage caused by LPS induced septic shock. Our data also suggest that the beneficial effects are in part due to the decrease in inflammatory cytokines and restoration of normal acetylation homeostasis. Chin Med J 2010;123(19):2682-2687