Objective:To investigate the effects of ketamine on production of Nitric oxide(NO),hydroxy radical(·OH) and superoxide anion(O2-·) in the rat alveolar macrophage cell line(NR8383) activated by Lipopolysaccharide(LPS). Methods:Macrophage was distributed into five groups,group C,group L,group K1,group K2 and group K3. Group L,K1,K2 and K3 were stimulated with LPS. Before stimulation,Group L,K1,K2 and K3 were treated with phosphate buffer solution(PBS),10,100 and 1 000 μmol/L ketamine. Group C was treated with PBS. The levels of NO,·OH and O2-· in the supernatant were assayed. Results:The concentration of NO,·OH and O2-· in group L was increased significantly(P < 0.01) when compared to Group C. The concentration of NO,·OH and O2-· in Group K2,K3 was obviously lower than those of Group L(P < 0.05). There was no statistical difference between K2 and K3(P > 0.05). Conclusions:Ketamine can inhibit LPS-induced production of NO,·OH and O2-·.