Radon inhalation activates antioxidative functions in some organs of mice. We examined the prevention effects of pre radon inhalation and the alleviation effects of post radon inhalation on carbon tetrachloride (CCl4)-induced oxidative damage in the brain, heart, lung, liver, and kidney of mice. In addition, we compared the effect of pre and post radon inhalation on oxidative damage. Mice inhaled radon at a concentration of 18000Bq/m3 for 6hrs before or after CCl4 administration. As a result, the total glutathione(t-GSH) contents and catalase(CAT) activities in the brain, heart, lung, liver, and kidney and superoxide dismutase(SOD) activities in the heart and lung were significantly higher in pre and post radon-inhaled mice than in mice treated with only CCl4. Pre radon inhalation inhibited and post radon inhalation reduced lipid peroxidation induced by CCl4. In addition, there were no significant differences in lipid peroxide(LPO) levels in the brain, heart, lung, liver, and kidney between pre and post radon-inhaled mice. These findings suggested that post radon inhalation has the same effects as pre radon inhalation against CCl4-induced oxidative damage in the brain, heart, lung, liver, and kidney.