Abstract: Objective To study combined toxic effect of formaldehyde and toluene exposure on oxidative damage of brain in mice.Methods The treatments were administered by static inhaling formaldehyde or/and toluene.The activity of superoxide dismutase(SOD),nitric oxide synthase(NOS),the contents of reactive oxygen species(ROS),glutathione (GSH),and malondialdehyde(MDA)in the brain of the mice were determined.Results When the mice were jointly exposed to formaldehyde and toluene,the contents of ROS and MDA,the activity of NOS in brain were increased and the contents of GSH and the activity of SOD were decreased(P<0.01).There were interactions between formaldehyde and toluene in ROS,NOS,SOD,GSH,and MDA(P<0.05).Conclusion Formaldehyde and toluene could induce oxidative damage in brain of mice.The joint toxicity of formaldehyde and toluene is synergistic.