This experiment was conducted to study the effects of dietary supplementation with N-acetylcysteine (NAC) on growth performance and plasma biochemical indices of piglets challenged by lipoplysaccharide (LPS). Twenty-four healthy piglets with the same genetic origin and similar body weight (11.58±0.26) kg were randomly allotted to 2 groups with 6 replicates per group and 2 piglets per replicate. The experiment lasted for 20 days. In the first 1～9 days, piglets in the control group were fed with basal diet and the others were fed with basal diet supplemented with 500 mg/kg NAC; in the next 10～20 days, one piglet of each replicate was fed alone and injected with 100 mg/kg LPS on the 10th, 13th and 20th day of the experiment, respectively, whereas the other one was injected with the same volume of sterile saline. The results showed that 1) dietary supplementation of NAC significantly relieved growth depression in piglets challenged by LPS (P<0.05); 2) dietary long-term supplementation with NAC increased the level of glutathione in plasma (P<0.01), and significantly increased the levels of plasma superoxide dismutase and EGF (P<0.05). The results above suggest that dietary supplementation with 500 mg/kg NAC could relieve the growth depression in piglets challenged by LPS.［Chinese Journal of Animal Nutrition, 2010，22（4）:1007-1011］