To examine effects of exogenous Cd on the kidney antioxidant defense system (AOS) and the possible protective role of Se against Cd toxicity, male Wistar albino rats (2 months old) were exposed during 30 days to oral intake of 200 ppm Cd (as CdCl2), 0.l ppm Se (as Na-selenite) or to the same doses of Cd / Se, simultaneously. Marked accumulation of Cd (23.44 +/- 0.69 micrograms/g w.m.) and marked alterations of AOS, resulting in kidney injury (renal pseudohypertrophy), were found in Cd-treated rats. Activities of total superoxide dismutase (SOC, EC 1.15.1.1), manganese-containing superoxide dismutase (MnSOD) and selenium-dependent glutathione peroxidase (Se GSH-Px, EG 1.11.1.9) were significantly reduced, whereas that of glutathione-S-transferase (CST, EC 2.5.1.18) and vitamin E (vit E) concentration were significantly increased in the kidneys of Cd-treated rats. Kidney catalase (CAT, EC 1.11.1.6) activity, ascorbic acid (AsA) and red blood cell glutathione (GSH, GSSG) levels were not markedly influenced by CD uptake. In kidneys of Se treated rats, the activities of total SOD, copper-zinc-containing superoxide dismutase (CuZnSOD) and GST were significantly increased Activities of kidney CAT and Se GSH-Px were largely unchanged, whereas significant increases of the kidney AsA and vit E concentrations occurred. In Cd + Se-cotreated rats, the kidney activities of MnSOD, CAT and Se GSH-Px, as well as vit E concentration, were the same as in controls, whereas CuZnSOD and GST activities and concentration of AsA exceeded normal values. These data indicate that Se only partially improves the AOS that is insufficient to prevent Cd-induced nephrotoxicity.