Plasma and erythrocyte selenium levels in rabbits supplemented with therapeutic doses of selenium were studied by Zeeman graphite furnace atomic absorption spectrometry using a new palladium-ascorbic acid chemical modifier in order to achieve a higher precision. An improved coupled test procedure was used to determine the glutathione peroxidase (GSH-Px) activities. Superoxide dismutase activities were measured employing a method for the clinical assay of the enzyme. The selenium levels and GSH-Px activities both in the plasma and erythrocytes were higher in the supplemented group when compared to the controls. The SOD activities were increased in the erythrocytes but remained unchanged in the plasma. Or the other hand, a higher copper/zinc ratio was found both in the plasma and erythrocytes of the supplemented group. These findings support the importance of the dietary selenium intake in terms of the principal role of selenium in the cellular antioxidative mechanisms and imply that measurements of plasma selenium levels may be a notable sensitive indicator of the short-term selenium status.