1. The purpose of this study was to correlate exercise induced changes of antioxidant enzymes with the distribution of mercury after mercury vapour exposure in mice. 2. Exercise training consisted of swimming (1 h/day for 5 days/week) for 9 weeks. After 9 weeks of training, swim-trained mice showed significantly elevated levels of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSHpx) in their red blood cells, CAT and GSHpx in their kidneys and SOD in the liver. 3. Exercised mice (Ex) and non-exercised mice (N.Ex) were exposed to mercury vapour (3.5 mg m-3) for 1 h. Mercury concentrations were assayed in the blood, brain, heart, lungs, liver and kidneys along with the mercury content of the entire body. The whole body mercury content showed no significant difference in any measurement (immediately, 24 h and 48 h after mercury exposure) between the Ex and N.Ex groups. Mercury concentrations in the Ex group were significantly higher than the N.Ex group in the heart, whole blood, red blood cells and the brain at 24 and 48 h; and in the plasma and kidneys at 24 h. 4. It was concluded that exercise training is a factor in distribution changes of mercury after exposure to mercury vapour, though it is not a factor in the total absorption and excretion of mercury.